Load Transducer System

ABSTRACT

A load transducer system is disclosed herein. The load transducer system includes a load transducer and a data processing device. The load transducer has a load transducer frame portion configured to elastically deform when a load is applied to the load transducer; and one or more deformation sensing elements, disposed on the load transducer frame portion, sensitive to one or more respective force or moment components of the load. The data processing device is operatively coupled to the one or more deformation sensing elements of the load transducer, the data processing device is configured to determine one or more output forces or moments from one or more respective output signals of the one or more deformation sensing elements, to determine one or more deformation compensation parameters for the load transducer system, and to correct the one or more output forces or moments using the one or more deformation compensation parameters.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of U.S. Nonprovisional patent applicationSer. No. 15/224,419, entitled “Load Transducer and Force MeasurementAssembly Using the Same”, filed on Jul. 29, 2016; which is acontinuation-in-part of U.S. Nonprovisional patent application Ser. No.14/714,797, entitled “Load Transducer and Force Measurement AssemblyUsing the Same”, filed on May 18, 2015, now U.S. Pat. No. 9,404,823;which is a continuation-in-part of U.S. Nonprovisional patentapplication Ser. No. 14/158,809, entitled “Low Profile Load Transducer”,filed on Jan. 18, 2014, now U.S. Pat. No. 9,032,817; and further claimsthe benefit of U.S. Provisional Patent Application No. 61/887,357,entitled “Low Profile Load Transducer”, filed on Oct. 5, 2013, thedisclosure of each of which is hereby incorporated by reference as ifset forth in their entirety herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not Applicable.

INCORPORATION BY REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISK

Not Applicable.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The field of the invention relates to multi-component load transducersutilizing multiple strain gage load channels for precise measurement offorces and moments and, more particularly, to load transducer systemsthat are capable of more accurately determining forces and moments bycorrecting the output signals of the load transducers for crosstalk,temperature-induced errors, and errors resulting from the position ofthe applied load.

2. Background and Related Art

The use of strain gages in load transducers to measure forces andmoments is a known art. A transducer can incorporate one or more loadchannels. Each load channel measures one of the load components, and iscomprised of one or more strain gages mounted to one or more elasticelements that deform under the applied load. An appropriate circuitryrelates the resistance change in each set of gages to the applied forceor moment. Strain gages have many industrial, medical, and electricalapplications due to their small size, low production cost, flexibilityin installation and use, and high precision.

A typical low profile, small, multi-component load transducer onlyfunctions correctly when the axial (i.e. vertical) force acts relativelycentral to the transducer. Specifications of such transducers indicate amaximum allowable offset for the force being approximately half thediameter of the transducer. Technical specifications of transducers aregiven as the allowable force and moment ratings, where the moment ratingis obtained by multiplying the maximum allowable force with the maximumallowable offset of the force.

Transducers can be used to measure forces and moments in linkages suchas those found in a robotic arm, where the links are connected byjoints, and the magnitude and offset of the forces transmitted by thesejoints are used to control the linkage. In such applications, it isdesirable to have a transducer which has significantly higher momentcapacity than those available in the market. Accordingly, there is aneed for an improved multi-component, low profile load transducer withhigh moment capacity.

When conventional load transducers are utilized in conjunction withforce plates, unique load transducers must be designed and fabricatedfor force plates having a particular footprint size. Consequently, inorder to fit force plates with varying footprint sizes, many differentcustom load transducers are required. These custom load transducerssignificantly increase the material costs associated with thefabrication of a force plate. Also, conventional load transducers oftenspan the full length or width of the force plate component to which theyare mounted, thereby resulting in elongate load transducers that utilizean excessive amount of stock material.

Therefore, what is needed is a load transducer that is capable of beinginterchangeably used with a myriad of different force plate sizes sothat load transducers that are specifically tailored for a particularforce plate size are unnecessary. Moreover, there is a need for auniversal load transducer that is compact and uses less stock materialthan conventional load transducers, thereby resulting in lower materialcosts. Furthermore, there is a need for a force measurement assemblythat utilizes the compact and universal load transducer thereon so as toresult in a more lightweight and portable force measurement assembly.

Also, certain strain gages or strain gage pairs of a typicalmulti-component load transducer are configured to be sensitive to aparticular component of the applied load (i.e., to a particular one ofthe force or moment components being measured). However, because thebody portion of a typical load transducer has unavoidable machiningimperfections, and the strain gages are not perfectly positioned on thebody of the load transducer, there is some crosstalk between thechannels of the load transducer. For example, a channel that is intendedto be sensitive only to the x-component of the force may also emit anon-zero output signal when only a vertical force is applied to the loadtransducer (i.e., when the z-component of the force is applied). Thus,in such a typical load transducer, there is undesirable crosstalkbetween the channels.

Moreover, the output of a typical multi-component load transducer isalso undesirably affected by the ambient temperature of the environmentin which the load transducer is disposed. For example, the accuracy of aload output signal of a load transducer that is disposed in a spacehaving a high ambient temperature (e.g., a space with a temperature of140 degrees or more) will be adversely affected by the high ambienttemperature. That is, high ambient temperature will introduceinaccuracies in the load output signal.

Furthermore, the position of the applied load may also adversely affectthe accuracy of the output signal of a typical multi-component loadtransducer. For example, when the load is applied at a location that isnear the periphery of the measurement surface of the load measurementdevice in which the load transducer is installed, the load output of theload transducer is often less accurate than when the load is appliedproximate to the center of the measurement surface of the loadmeasurement device. As such, the measurement accuracy of a typical loadmeasurement device undesirably varies depending upon the position of theload applied thereto.

Therefore, what is also needed is a load transducer system that iscapable of correcting the output signal of a load transducer so as toreduce or eliminate the effects of crosstalk among the channels of theload transducer. In addition, there is a need for a load transducersystem that is capable of correcting the output signal of a loadtransducer so as to reduce or eliminate the effects of changes intemperature on the output of the load transducer. Further, there is aneed for a load transducer system that is capable of accuratelydetermining the applied load regardless of the location of the appliedload being measured by the load transducer.

BRIEF SUMMARY OF EMBODIMENTS OF THE INVENTION

Accordingly, the present invention is directed to a load transducersystem that substantially obviates one or more problems resulting fromthe limitations and deficiencies of the related art.

In accordance with one or more embodiments of the present invention,there is provided a load transducer system that comprises a loadtransducer, which includes a load transducer frame portion, the loadtransducer frame portion configured to elastically deform when a load isapplied to the load transducer, and one or more deformation sensingelements disposed on the load transducer frame portion, the one or moredeformation sensing elements being sensitive to one or more respectiveforce or moment components of the load and outputting one or morerespective output signals representative of the one or more respectiveforce or moment components of the load; and a data processing deviceoperatively coupled to the one or more deformation sensing elements ofthe load transducer, the data processing device configured to receivethe one or more respective output signals from the one or moredeformation sensing elements, the data processing device furtherconfigured to determine one or more respective output forces or momentsfrom one or more respective output signals, and the data processingdevice additionally configured to determine one or more deformationcompensation parameters for the load transducer system and to correctthe one or more respective output forces or moments using the one ormore deformation compensation parameters.

In a further embodiment of the present invention, the load transducersystem further comprises one or more additional deformation sensingelements disposed on the load transducer, the one or more additionaldeformation sensing elements configured to output one or moredeformation output signals indicative of a deformation of a portion ofthe load transducer, the one or more additional deformation sensingelements being operatively to the data processing device, the dataprocessing device configured to receive the one or more respectivedeformation output signals from the one or more additional deformationsensing elements, and to determine the one or more deformationcompensation parameters based upon the one or more respectivedeformation output signals.

In yet a further embodiment, the one or more additional deformationsensing elements of the load transducer comprise one or more straingages configured to measure the deformation of the portion of the loadtransducer.

In still a further embodiment, the load transducer frame portion is inthe form of a load cell pylon, the load cell pylon being compact and ofone-piece construction.

In yet a further embodiment, the data processing device is furtherconfigured to determine one or more temperature compensation parametersfor the load transducer system and to correct at least one of the one ormore respective output signals using the one or more temperaturecompensation parameters, the data processing device additionallyconfigured to determine at least one output force or moment from thecorrected one or more respective output signals of the one or moredeformation sensing elements of the load transducer.

In still a further embodiment, the load transducer system furthercomprises one or more redundant deformation sensing elements, the one ormore redundant deformation sensing elements configured to enable theload transducer to produce the same output when one of the one or moredeformation sensing elements experiences a failure.

In accordance with one or more other embodiments of the presentinvention, there is provided a load transducer system that comprises aload transducer, which includes a load transducer frame portion, theload transducer frame portion configured to elastically deform when aload is applied to the load transducer, and one or more deformationsensing elements disposed on the load transducer frame portion, the oneor more deformation sensing elements being sensitive to one or morerespective force or moment components of the load and outputting one ormore respective output signals representative of the one or morerespective force or moment components of the load; and a data processingdevice operatively coupled to the one or more deformation sensingelements of the load transducer, the data processing device configuredto receive the one or more respective output signals from the one ormore deformation sensing elements, the data processing device furtherconfigured to determine one or more temperature compensation parametersfor the load transducer system and to correct the one or more respectiveoutput signals from the one or more deformation sensing elements usingthe one or more temperature compensation parameters, the data processingdevice additionally configured to determine one or more respectiveoutput forces or moments from one or more corrected respective outputsignals.

In a further embodiment of the present invention, the load transducersystem further comprises one or more temperature sensing elementsdisposed on the load transducer, the one or more temperature sensingelements configured to output one or more temperature output signalsindicative of a temperature of at least a portion of the loadtransducer, the one or more temperature sensing elements beingoperatively coupled to the data processing device, the data processingdevice configured to receive the one or more respective temperatureoutput signals from the one or more temperature sensing elements, and todetermine the one or more temperature compensation parameters based uponthe one or more respective temperature output signals.

In yet a further embodiment, the one or more temperature sensingelements comprise one or more thermistors.

In still a further embodiment, the one or more temperature sensingelements comprise one or more strain gages.

In yet a further embodiment, the data processing device is furtherconfigured to determine one or more excitation current values associatedwith the one or more deformation sensing elements of the loadtransducer, and to determine the one or more temperature compensationparameters based upon the one or more excitation current values.

In still a further embodiment, the data processing device utilizes theone or more temperature compensation parameters to correct fortemperature-induced effects on the zero drift of the load transducer.

In yet a further embodiment, the data processing device utilizes the oneor more temperature compensation parameters to correct fortemperature-induced effects on the sensitivity of the load transducer.

In accordance with yet one or more other embodiments of the presentinvention, there is provided a load transducer system that comprises aload transducer, which includes a load transducer frame portion, theload transducer frame portion configured to elastically deform when aload is applied to the load transducer, and one or more deformationsensing elements disposed on the load transducer frame portion, the oneor more deformation sensing elements being sensitive to one or morerespective force or moment components of the load and outputting one ormore respective output signals representative of the one or morerespective force or moment components of the load; and a data processingdevice operatively coupled to the one or more deformation sensingelements of the load transducer, the data processing device configuredto receive the one or more respective output signals from the one ormore deformation sensing elements, the data processing device furtherconfigured to reference a stored calibration matrix for the loadtransducer, and to determine one or more output forces or moments fromthe one or more respective output signals of the one or more deformationsensing elements using the stored calibration matrix, the dataprocessing device additionally configured to determine a position of theapplied load, and to correct the one or more output forces or momentsbased upon the position of the applied load.

In a further embodiment of the present invention, the data processingdevice is configured to correct the one or more output forces or momentsby utilizing a mathematical relationship that is based upon the positionof the applied load.

From the foregoing disclosure and the following more detaileddescription of various preferred embodiments it will be apparent tothose skilled in the art that the present invention provides asignificant advance in the technology and art of load transducers.Particularly significant in this regard is the potential the inventionaffords for providing a load transducer system that compensates forvarious operating conditions so as to produce more accuratemeasurements. Additional features and advantages of various preferredembodiments will be better understood in view of the detaileddescription provided below.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The invention will now be described, by way of example, with referenceto the accompanying drawings, in which:

FIG. 1 is a perspective view of a low profile load transducer, accordingto a first embodiment of the invention;

FIG. 2 is a first side view of the low profile load transducer of FIG.1, according to the first embodiment of the invention;

FIG. 3 is a second side view of the low profile load transducer of FIG.1, according to the first embodiment of the invention;

FIG. 4 is a top view of the low profile load transducer of FIG. 1,according to the first embodiment of the invention;

FIG. 5 is a block diagram illustrating data manipulation operationscarried out by the load transducer data processing system, according toan embodiment of the invention;

FIG. 6 is a perspective view of a low profile load transducer, accordingto a second embodiment of the invention;

FIG. 7 is a first side view of the low profile load transducer of FIG.6, according to the second embodiment of the invention;

FIG. 8 is a second side view of the low profile load transducer of FIG.6, according to the second embodiment of the invention;

FIG. 9 is a top view of the low profile load transducer of FIG. 6,according to the second embodiment of the invention;

FIG. 10 is a perspective view of a low profile load transducer,according to a third embodiment of the invention;

FIG. 11 is a first side view of the low profile load transducer of FIG.10, according to the third embodiment of the invention;

FIG. 12 is a second side view of the low profile load transducer of FIG.10, according to the third embodiment of the invention;

FIG. 13 is a top view of the low profile load transducer of FIG. 10,according to the third embodiment of the invention;

FIG. 14 is a bottom view of the low profile load transducer of FIG. 10,according to the third embodiment of the invention;

FIG. 15 is a perspective view of a low profile load transducer,according to a fourth embodiment of the invention;

FIG. 16 is a first side view of the low profile load transducer of FIG.15, according to the fourth embodiment of the invention;

FIG. 17 is a second side view of the low profile load transducer of FIG.15, according to the fourth embodiment of the invention;

FIG. 18 is a top view of the low profile load transducer of FIG. 15,according to the fourth embodiment of the invention;

FIG. 19 is a perspective view of a low profile load transducer,according to a fifth embodiment of the invention;

FIG. 20 is a perspective view of a low profile load transducer,according to a sixth embodiment of the invention;

FIG. 21 is a perspective view of a low profile load transducer,according to a seventh embodiment of the invention;

FIG. 22 is a perspective view of a low profile load transducer,according to an eighth embodiment of the invention;

FIG. 23 is a perspective view of a low profile load transducer,according to a ninth embodiment of the invention;

FIG. 24 is a perspective view of a low profile load transducer,according to a tenth embodiment of the invention;

FIG. 25 is a perspective view of an exemplary mounting arrangement forthe low profile load transducer illustrated in FIGS. 15-18;

FIG. 26 is a top perspective view of a load transducer, according to aneleventh embodiment of the invention;

FIG. 27 is a first side view of the load transducer of FIG. 26,according to the eleventh embodiment of the invention;

FIG. 28 is a second side view of the load transducer of FIG. 26,according to the eleventh embodiment of the invention;

FIG. 29 is a bottom perspective view of the load transducer of FIG. 26,according to the eleventh embodiment of the invention;

FIG. 30 is a top perspective view of a load transducer, according to atwelfth embodiment of the invention;

FIG. 31 is a first side view of the load transducer of FIG. 30,according to the twelfth embodiment of the invention;

FIG. 32 is a second side view of the load transducer of FIG. 30,according to the twelfth embodiment of the invention;

FIG. 33 is a bottom perspective view of the load transducer of FIG. 30,according to the twelfth embodiment of the invention;

FIG. 34 is a perspective view of a force measurement system thatutilizes the load transducer of FIG. 30, according to an embodiment ofthe invention;

FIG. 35 is a bottom, assembled perspective view of the force measurementassembly of the force measurement system of FIG. 34;

FIG. 36 is a bottom, partially exploded perspective view of the forcemeasurement assembly of the force measurement system of FIG. 34;

FIG. 37 is a block diagram of constituent components of the forcemeasurement systems of FIGS. 34 and 42;

FIG. 38 is a block diagram illustrating data manipulation operationscarried out by the force measurement systems of FIGS. 34 and 42;

FIG. 39 is a top perspective view of a load transducer, according to athirteenth embodiment of the invention;

FIG. 40 is a side view of the load transducer of FIG. 39, according tothe thirteenth embodiment of the invention;

FIG. 41 is a top plan view of the load transducer of FIG. 39, accordingto the thirteenth embodiment of the invention;

FIG. 42 is a bottom, assembled perspective view of a force measurementsystem that utilizes the load transducer of FIG. 39, according to anembodiment of the invention;

FIG. 43 is a bottom, partially exploded perspective view of the forcemeasurement assembly of the force measurement system of FIG. 42;

FIG. 44 is a top perspective view of a load transducer, according to afourteenth embodiment of the invention;

FIG. 45 is a side view of the load transducer of FIG. 44, according tothe fourteenth embodiment of the invention;

FIG. 46 is a top plan view of the load transducer of FIG. 44, accordingto the fourteenth embodiment of the invention;

FIG. 47 is a top perspective view of a load transducer, according to afifteenth embodiment of the invention, wherein the load transducer ofFIG. 47 is configured for a left side mounting arrangement on the forcemeasurement assembly;

FIG. 48 is a top perspective view of a load transducer that is generallysimilar to the load transducer of FIG. 47, except that the loadtransducer of FIG. 48 is configured for a right side mountingarrangement on the force measurement assembly rather than a left sidemounting arrangement;

FIG. 49 is a bottom, assembled perspective view of a force measurementassembly that utilizes the load transducers of FIGS. 47 and 48,according to another embodiment of the invention;

FIG. 50 is a bottom, partially exploded perspective view of the forcemeasurement assembly of FIG. 49;

FIG. 51 is a top perspective view of a load transducer, according to asixteenth embodiment of the invention;

FIG. 52 is a first side view of the load transducer of FIG. 51,according to the sixteenth embodiment of the invention;

FIG. 53 is a second side view of the load transducer of FIG. 51,according to the sixteenth embodiment of the invention;

FIG. 54 is a top plan view of the load transducer of FIG. 51, accordingto the sixteenth embodiment of the invention;

FIG. 55 is a perspective view of a load transducer, according to aseventeenth embodiment of the invention;

FIG. 56 is a front elevational view of the load transducer of FIG. 55;

FIG. 57 is a rear elevational view of the load transducer of FIG. 55;

FIG. 58 is a side view of the load transducer of FIG. 55;

FIG. 59 is a top view of the load transducer of FIG. 55;

FIG. 60 is a transverse cross-sectional view of the load transducer ofFIG. 55, wherein the transverse section is cut through the cutting planeline A-A in FIG. 56;

FIG. 61 is a perspective view of a load transducer, according to aneighteenth embodiment of the invention;

FIG. 62 is a front elevational view of the load transducer of FIG. 61;

FIG. 63 is a rear elevational view of the load transducer of FIG. 61;

FIG. 64 is a side view of the load transducer of FIG. 61;

FIG. 65 is a top view of the load transducer of FIG. 61;

FIG. 66 is a transverse cross-sectional view of the load transducer ofFIG. 61, wherein the transverse section is cut through the cutting planeline B-B in FIG. 62;

FIG. 67 is a block diagram illustrating data manipulation operationscarried out by the load transducer data processing system, according toan embodiment of the invention;

FIG. 68 is a block diagram of constituent components of the loadtransducer system, which utilizes the load transducer of FIG. 55 or FIG.61, according to an embodiment of the invention; and

FIG. 69 is a signal flow diagram for the load transducer systemdescribed herein, which utilizes the load transducer of FIG. 55 or FIG.61, according to an embodiment of the invention.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variouspreferred features illustrative of the basic principles of theinvention. The specific design features of the load transducers asdisclosed herein, including, for example, specific dimensions,orientations, locations, and shapes of the various components, will bedetermined in part by the particular intended application and useenvironment. Certain features of the illustrated embodiments have beenenlarged or distorted relative to others to facilitate visualization andclear understanding. In particular, thin features may be thickened, forexample, for clarity or illustration. All references to direction andposition, unless otherwise indicated, refer to the orientation of theload transducers illustrated in the drawings. In general, up or upwardgenerally refers to an upward direction within the plane of the paper inFIG. 1 and down or downward generally refers to a downward directionwithin the plane of the paper in FIG. 1.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

It will be apparent to those skilled in the art, that is, to those whohave knowledge or experience in this area of technology, that many usesand design variations are possible for the improved load transducersdisclosed herein. The following detailed discussion of variousalternative and preferred embodiments will illustrate the generalprinciples of the invention. Other embodiments suitable for otherapplications will be apparent to those skilled in the art given thebenefit of this disclosure.

Referring now to the drawings, FIGS. 1-4 illustrate a load transducer 10according to a first exemplary embodiment of the present invention. Thisload transducer 10 is designed to have a low profile, small size,trivial weight, high sensitivity, and easy manufacturability. The loadtransducer 10 generally includes a one-piece compact transducer frame 12having a central body portion 14 and a plurality of beams 16, 18, 20,22, 24, 26, 28, 30 extending outwardly from the central body portion 14.As best illustrated in the perspective view of FIG. 1, each of the beams16, 18, 20, 22, 24, 26, 28, 30 comprises a respective load cell ortransducer element for measuring forces and/or moments. For example, theload cells of beams 16, 18, 24, 26 are configured to respectivelymeasure the forces F1, F2, F3, F4 with force vector components F1 _(x),F1 _(y), F1 _(z), F2 _(x), F2 _(y), F2 _(z), F3 _(x), F3 _(y), F3 _(z),F4 _(x), F4 _(y), F4 _(z). In addition to forces, the output of the loadcells can also be used to determine moments and the point of applicationof a force (i.e., its center of pressure). Referring again to FIG. 1, itcan be seen that the illustrated load transducer 10 comprises eightsingle or multi-axis load cells that are mounted to a common structureor body portion 14.

The illustrated transducer frame 12 is shown in FIGS. 1-4. Theillustrated transducer frame 12 includes the central body portion 14 anda plurality of beams 16, 18, 20, 22, 24, 26, 28, 30 extending outwardlytherefrom. In the illustrated embodiment, the transducer frame 12 ismilled as one solid and continuous piece of a single material. That is,the transducer frame 12 is of unitary or one-piece construction with thebody portion 14 and the beams 16, 18, 20, 22, 24, 26, 28, 30 integrallyformed together. The transducer frame 12 is preferably machined in onepiece from aluminum, titanium, steel, or any other suitable materialthat meets strength and weight requirements. Alternatively, the beams16, 18, 20, 22, 24, 26, 28, 30 can be formed separately and attached tothe body portion 14 in any suitable manner.

With reference to FIG. 1, it can be seen that the illustrated centralbody portion 14 is generally in the form of rectangular prism (i.e., asquare prism) with substantially planar top, bottom, and side surfaces.In FIG. 1, it can be seen that the body portion 14 comprises a firstpair of opposed sides 14 a, 14 c and a second pair of opposed sides 14b, 14 d. The side 14 a is disposed generally parallel to the side 14 c,while the side 14 b is disposed generally parallel to the side 14 d.Each of the sides 14 a, 14 b, 14 c, 14 d is disposed generallyperpendicular to the planar top and bottom surfaces. Also, each of thefirst pair of opposed sides 14 a, 14 c is disposed generallyperpendicular to each of the second pair of opposed sides 14 b, 14 d.While not explicitly shown in FIGS. 1-4, the central body portion 14 maycomprise one or more apertures disposed therethrough for accommodatingfasteners (e.g., screws) that attach electronics or circuitry to thebody portion 14. In addition to fasteners, it is noted that any othersuitable means for attachment of the electronics or circuitry canalternatively be utilized (e.g., suitable adhesives, etc.). While theillustrated body portion 14 is generally in the form of a square prism,it is to be understood that the body portion 14 can alternatively haveother suitable shapes.

As shown in FIGS. 1-4, the illustrated beams 16, 18, 20, 22, 24, 26, 28,30 are each attached to one of the sides 14 a, 14 b, 14 c, 14 d of thebody portion 14, and extend generally horizontally outward therefrom. Inparticular, beams 16, 18 extend generally horizontally outward from side14 a of the body portion 14, beams 20, 22 extend generally horizontallyoutward from side 14 b of the body portion 14, beams 24, 26 extendgenerally horizontally outward from side 14 c of the body portion 14,and beams 28, 30 extend generally horizontally outward from side 14 d ofthe body portion 14. In addition, each of the illustrated beams 16, 18,20, 22, 24, 26, 28, 30 extend substantially parallel to the top andbottom surfaces of the body portion 14. Each of the illustrated beams16, 18, 20, 22, 24, 26, 28, 30 has a cantilevered end relative to thebody portion 14 that allows for deflection of the ends of the beams 16,18, 20, 22, 24, 26, 28, 30 in the vertical direction.

With particular reference to FIGS. 1 and 4, it can be seen that thebeams 16, 18 extending from side 14 a are substantially parallel to oneanother, and laterally spaced apart from one another by a gap. Opposedbeams 24, 26, which extend from side 14 c, also are substantiallyparallel to one another, and laterally spaced apart from one another bya gap. Beam 16 extends in a longitudinal direction that is generallyco-linear with, but opposite to the extending direction of beam 26(i.e., both beams 16 and 26 are aligned along central longitudinal axisLA1). Similarly, beam 18 extends in a longitudinal direction that isgenerally co-linear with, but opposite to the extending direction ofbeam 24 (i.e., both beams 18 and 24 are aligned along centrallongitudinal axis LA2). The beams 20, 22 extending from side 14 b aresubstantially parallel to one another, and laterally spaced apart fromone another by a gap. Opposed beams 28, 30, which extend from side 14 d,also are substantially parallel to one another, and laterally spacedapart from one another by a gap. Beam 20 extends in a longitudinaldirection that is generally co-linear with, but opposite to theextending direction of beam 30 (i.e., both beams 20 and 30 are alignedalong central longitudinal axis LA3). Similarly, beam 22 extends in alongitudinal direction that is generally co-linear with, but opposite tothe extending direction of beam 28 (i.e., both beams 22 and 28 arealigned along central longitudinal axis LA4). The illustrated beams 16,18, 20, 22, 24, 26, 28, 30 are provided with generally verticallyextending apertures 32 near their ends for accommodating fasteners thatare used to secure the load transducer 10 to additional structures.Although, it is noted that any other suitable means for attachment ofthe load transducer 10 can alternatively be utilized (e.g., a suitableadhesive for attaching metallic components to one another).

The main body portions of illustrated beams 16, 18, 20, 22, 24, 26, 28,30 have a rectangular-shaped cross section to form generally planar,opposed top and bottom surfaces, and generally planar, opposed sidesurfaces for attachment of load cell components as describedhereinafter. The illustrated beams 16, 18, 20, 22, 24, 26, 28, 30 havegenerally cylindrical end portions, which include the fastener apertures32. As best shown in FIG. 1, the illustrated top planar surfaces of thebeam main body portions of beams 16, 18, 24, 26 are recessed below thetop surfaces of the beam cylindrical end portions to protect the loadcell components from engagement with the structure to which the loadtransducer 10 is attached, while the illustrated bottom planar surfacesof the beam main body portions of beams 20, 22, 28, 30 are recessedabove the bottom surfaces of the beam cylindrical end portions toprotect the load cell components from engagement with the structure towhich the load transducer 10 is attached. In other words, as shown inFIG. 1, the cylindrical end portions of beams 16, 18, 24, 26 areprovided with a top standoff portion (i.e., a cylindrical portionprotruding from the top of each beam having the aperture 32), while thecylindrical end portions of beams 20, 22, 28, 30 are provided with abottom standoff portion (i.e., a cylindrical portion protruding from thebottom of each beam having the aperture 32). While not explicitly shownin the figures, beams 16, 18, 20, 22, 24, 26, 28, 30 may also includeapertures disposed therethrough for increasing the deflectability of thebeams 16, 18, 20, 22, 24, 26, 28, 30 as desired (e.g., the aperturescould be disposed below, or adjacent to each of the strain gages 34, 36,38). In order to accommodate these apertures, the length of each beam16, 18, 20, 22, 24, 26, 28, 30 could be extended so that multiple straingages 34, 36 on a common beam could be spaced apart from one anotheralong a length of the beam (i.e., each strain gage 34, 36 would occupy adedicated, respective segment of the beam). It is noted that theseapertures can be of any suitable size and shape as needed and also canbe eliminated if desired. It is further noted that the beams 16, 18, 20,22, 24, 26, 28, 30 can alternatively have other cross-sectional shapesdepending on whether it is desired to have planar surfaces at the topand/or bottom or left and/or right sides for the load cell componentsbut the illustrated rectangular shape is particularly desirable becausethe same frame can be used for multiple configurations of the transducerload cells.

The illustrated one-piece frame 12 has a low profile or is compact. Theterms “low profile” and “compact” are used in this specification and theclaims to mean that the height is substantially smaller than thefootprint dimensions so that the load transducer 10 can be utilized in amechanical joint without significant changes to the mechanical joint.The illustrated one piece frame 12 has a height H that is about 20% itsfootprint width W₁ or W₂ (see FIGS. 2, 3, 7, and 8). As a result, theload transducer 10 has a low profile or is compact and has a height Hthat is about 20% its footprint width W₁ or W₂. The term “load cell” isused in the specification and claims to mean a load sensing element ofthe load transducer that is capable of sensing one or more loadcomponents of the applied load.

As best shown in FIG. 1, the illustrated load cells are located on beams16, 18, 20, 24, 26, and 30. In the illustrated embodiment, beams 22, 28do not contain any load cells, but, in other embodiments, may containload cells with strain gages 38 similar to beams 20, 30. Beams 16, 26also may contain strain gages 36, similar to beams 18, 24, in otherembodiments. In a preferred embodiment, each load cell comprises one ormore strain gages 34, 36, 38. Specifically, in the illustratedembodiment, beams 16, 18, 24, 26 each comprise a strain gage 34 disposedon the top surface thereof that is sensitive to the vertical forcecomponent (i.e., a F_(z) strain gage). Opposed beams 18, 24 also eachcomprise a strain gage 36 disposed on a side surface thereof that issensitive to a first shear force component (i.e., a F_(X) strain gage).Opposed beams 20, 30 each comprise a strain gage 38 disposed on a sidesurface thereof that is sensitive to a second shear force component(i.e., a F_(Y) strain gage). All eight (8) of the strain gages 34, 36,38 are measuring a difference in the bending moments in the beams. Ifthe applied shears to each of the two parallel beams 18, 24 or 20, 30are equal (which is most likely the case), this is an optimal number ofstrain gages for a six-component load transducer (i.e., for a loadtransducer that is capable of measuring the three (3) force componentsF_(X), F_(Y), F_(Z) and the three (3) moment components M_(X), M_(Y),M_(Z)). Shear web gages can also be used in lieu of one or more of theillustrated strain gages 34, 36, 38. Also, in other preferredembodiments alternate load and/or moment sensors may be utilized asrequired or desired as long as they do not interfere with the advantagesof the design as a whole. For example, piezoelectric gages orHall-effect sensors are possible alternatives to the strain gages 34,36, 38.

As best shown in FIG. 1, the illustrated load cells are configured asbending beam load cells. The illustrated strain gages 34, 36, 38 aremounted to either top or side surfaces of the beams 16, 18, 20, 24, 26,30 between their attachment locations to the body portion 14 and thecylindrical end portions thereof. Alternatively, the strain gages 34 canbe mounted to the bottom surfaces of the beams 16, 18, 24, 26 betweentheir attachment locations to the body portion 14 and the cylindricalend portions thereof, while the strain gages 36, 38 can be mounted tothe opposite side surfaces of the beams 18, 20, 24, 30 between theirattachment locations to the body portion 14 and the cylindrical endportions thereof. That is, the strain gages 34, 36, 38 are mounted tosurfaces generally normal to the direction of applied vertical and/orshear forces (i.e., F_(X), F_(Y), F_(Z)). It is also noted thatalternatively, the strain gages 34 can be mounted at both the topsurface and the bottom surface of the beams 16, 18, 24, 26, and/or thestrain gages 36, 38 can be mounted at both opposed side surfaces of thebeams 18, 20, 24, 30. These strain gages 34, 36, 38 measure force eitherby bending moment or difference of bending moments at two crosssections. As force is applied to the ends of the beams (e.g., forces F1,F2, F3, F4 with force vector components F1 _(x), F1 _(y), F1 _(z), F2_(x), F2 _(y), F2 _(z), F3 _(x), F3 _(y), F3 _(z), F4 _(x), F4 _(y), F4_(z) applied to the ends of respective beams 16, 18, 24, 26), the beams16, 18, 20, 24, 26, 30 with strain gages attached thereto bend. Thisbending either stretches or compresses the strain gages 34, 36, 38, inturn changing the resistances of the electrical currents passingtherethrough. The amount of change in the electrical voltage or currentis proportional to the magnitude of the applied force (e.g., forces F1,F2, F3, F4 with force vector components F1 _(x), F1 _(y), F1 _(z), F2_(x), F2 _(y), F2 _(z), F3 _(x), F3 _(y), F3 _(z), F4 _(x), F4 _(y), F4_(z) applied to the ends of respective beams 16, 18, 24, 26).

Alternatively, the load cells can be configured as shear-web load cells.In this configuration, the strain gages are mounted to either one of thelateral side surfaces of the beams between their attachment locations tothe body portion 14 and the cylindrical end portions thereof. It isnoted that alternatively, the strain gages can be mounted at both of thelateral side surfaces of the beams. Mounted in these positions, thestrain gages directly measure shear as force is applied to the end ofthe beam.

As best shown in FIG. 1, the load transducer 10 measures applied forces(e.g., forces F1, F2, F3, F4 with force vector components F1 _(x), F1_(y), F1 _(z), F2 _(x), F2 _(y), F2 _(z), F3 _(x), F3 _(y), F3 _(z), F4_(x), F4 _(y), F4 _(z) applied to the ends of respective beams 16, 18,24, 26) at each of the load cells. The sum of the forces is the forcebeing applied to any assembly attached to the top of the load transducer10. The load cells of the beams 16, 26 measure the force being appliedto one lateral side of the load transducer 10; whereas, load cells ofthe beams 18, 24 measure the force being applied to the other lateralside of the load transducer 10. The various moments are determined bysubtracting the sum total of the forces acting on one pair of load cellsfrom the sum total acting upon the opposite pair. For example,subtracting the sum total of the forces acting on load cell of beam 16and load cell of beam 18 from the sum total of the forces acting on loadcell of beam 24 and load cell of beam 26, subtracting the sum total ofload cells of beams 18, 24 from the sum total of load cells of beams 16,26.

The sensory information from the strain gages 34, 36, 38 is transmittedto a microprocessor which could then be used to control the assembly towhich the load transducer is a part of such as a robotic assembly. Asbest shown in FIG. 1, the planar central body portion 14 of thetransducer frame 12 provides an area where associated electronics and/orcircuitry can be mounted. Alternatively, the electronics and/orcircuitry can be mounted at any other suitable location. FIG. 5schematically illustrates exemplary electronic components that can beincluded in the load transducer data processing system. The strain gages34, 36, 38 of load transducer 10 may be electrically connected to asignal amplifier/converter 40, which in turn, is electrically connectedto a computer 42 (i.e., a data acquisition and processing device or adata processing device with a microprocessor). The components 10, 40, 42of the system may be connected either by wiring, or wirelessly to oneanother.

FIG. 5 graphically illustrates the acquisition and processing of theload data carried out by the exemplary load transducer data processingsystem. Initially, as shown in FIG. 5, external forces F1-F4 and/ormoments are applied to the load transducer 10. When the electricalresistance of each strain gage 34, 36, 38 is altered by the applicationof the applied forces and/or moments, the change in the electricalresistance of the strain gages brings about a consequential change inthe output voltage of the strain gage bridge circuit (e.g., a Wheatstonebridge circuit). Thus, in one embodiment, the eight (8) strain gages 34,36, 38 output a total of eight (8) analog output voltages (signals). Insome embodiments, the eight (8) analog output voltages from the eight(8) strain gages 34, 36, 38 are then transmitted to a preamplifier board(not shown) for preconditioning. The preamplifier board is used toincrease the magnitudes of the analog voltage signals, and preferably,to convert the analog voltage signals into digital voltage signals aswell. After which, the load transducer 10 transmits the output signalsS_(TO1)-S_(TO8) to a main signal amplifier/converter 40. Depending onwhether the preamplifier board also includes an analog-to-digital (A/D)converter, the output signals S_(TO1)-S_(TO8) could be either in theform of analog signals or digital signals. The main signalamplifier/converter 40 further magnifies the transducer output signalsS_(TO1)-S_(TO8), and if the signals S_(TO1)-S_(TO8) are of theanalog-type (for a case where the preamplifier board did not include ananalog-to-digital (A/D) converter), it may also convert the analogsignals to digital signals. Then, the signal amplifier/converter 40transmits either the digital or analog signals S_(ACO1)-S_(ACO8) to thedata acquisition/data processing device 42 (computer 42) so that theforces and/or moments that are being applied to the load transducer 10can be transformed into output load values OL. The computer or dataacquisition/data processing device 42 may further comprise ananalog-to-digital (A/D) converter if the signals S_(ACO1)-S_(ACO8) arein the form of analog signals. In such a case, the analog-to-digitalconverter will convert the analog signals into digital signals forprocessing by the microprocessor of the computer 42.

When the computer or data acquisition/data processing device 42 receivesthe voltage signals S_(ACO1)-S_(ACO8), it initially transforms thesignals into output forces and/or moments by multiplying the voltagesignals S_(ACO1)-S_(AC08) by a calibration matrix. After which, theforce components F_(X), F_(Y), F_(Z) and the moment components M_(X),M_(Y), M_(Z) applied to the load transducer 10 are determined by thecomputer or data acquisition/data processing device 42. Also, the centerof pressure (i.e., the x and y coordinates of the point of applicationof the force applied to the load transducer 10) can be determined by thecomputer or data acquisition/data processing device 42.

FIGS. 6-9 illustrate a load transducer 10′ according to a secondexemplary embodiment of the present invention. With reference to thesefigures, it can be seen that, in some respects, the second exemplaryembodiment is similar to that of the first embodiment. Moreover, someparts are common to both such embodiments. For the sake of brevity, theparts that the second embodiment of the load transducer has in commonwith the first embodiment will only be briefly mentioned, if at all,because these components have already been explained in detail above.Furthermore, in the interest of clarity, these components will bedenoted using the same reference characters that were used in the firstembodiment.

Initially, referring to the perspective view of FIG. 6, it can be seenthat, like the first exemplary embodiment, the transducer frame 12′ ofthe second embodiment includes a central body portion 14 and a pluralityof beams 16, 18, 20′, 24′, 28, 30 extending outwardly therefrom.Although, unlike the first exemplary embodiment of the load transducer,the side 14 b of the body portion 14 of the load transducer 10′ containsonly a single beam 20′ extending therefrom, rather two beams 20, 22 (seeFIG. 1). Similarly, unlike the load transducer 10 of the firstembodiment, the side 14 c of the body portion 14 of the load transducer10′ contains only a single beam 24′ extending therefrom, rather twobeams 24, 26 (refer to FIG. 1). Also, unlike the load transducer 10 ofthe first embodiment, the load transducer 10′ includes only three straingages 34 that are sensitive to the vertical force component (i.e., threeF_(Z) strain gages), rather than four strain gages.

In particular, in the second embodiment, beams 16, 18, 24′ each comprisea strain gage 34 disposed on the top surface thereof that is sensitiveto the vertical force component (i.e., a F_(Z) strain gage). Beams 18,24′ also each comprise a strain gage 36 disposed on a side surfacethereof that is sensitive to a first shear force component (i.e., aF_(X) strain gage), while beams 20′, 30 each comprise a strain gage 38disposed on a side surface thereof that is sensitive to a second shearforce component (i.e., a F_(Y) strain gage). The load transducer 10′ ofthe second embodiment is capable of measuring the three force components(F_(X), F_(Y), F_(Z)) and the three moment components (M_(X), M_(Y),M_(Z)) with a minimum of six beams 16, 18, 20′, 24′, 28, 30 (i.e., threeinput beams and three output beams) and a minimum of seven strain gages34, 36, 38.

Now, with reference to the top view illustrated in FIG. 9, it can beseen that the central longitudinal axis LA5 of the beam 20′, whichextends from side 14 b of the body portion 14, is generally equallyspaced apart from the central longitudinal axis LA3 and LA4 (i.e., thecentral longitudinal axis LA5 of the beam 20′ is generally centeredbetween the central longitudinal axis LA3 of beam 30 and the centrallongitudinal axis LA4 of beam 28). Similarly, as shown in FIG. 9, thelongitudinal axis LA6 of the beam 24′, which extends from side 14 c ofthe body portion 14, is generally equally spaced apart from the centrallongitudinal axis LA1 and LA2 (i.e., the central longitudinal axis LA6of the beam 24′ is generally centered between the central longitudinalaxis LA1 of beam 16 and the central longitudinal axis LA2 of beam 18).The other features of the load transducer 10′ are similar to that of theload transducer 10, and thus, need not be reiterated herein.

FIGS. 10-14 illustrate a load transducer 100 according to a thirdexemplary embodiment of the present invention. Referring initially tothe perspective view of FIG. 10, it can be seen that the load transducer100 generally includes a one-piece compact transducer frame 112 having acentral body portion 114 and a plurality of generally U-shapedtransducer beams 116, 118, 120, 122 extending outwardly from the centralbody portion 114. As best illustrated in FIG. 10, each of the beams 116,118, 120, 122 comprises a plurality of load cells or transducer elementsfor measuring forces and/or moments.

With reference again to FIG. 10, it can be seen that the illustratedcentral body portion 114 is generally in the form of square band-shapedelement with a central opening 102 disposed therethrough. In FIG. 10, itcan be seen that the body portion 114 comprises a first pair of opposedsides 114 a, 114 c and a second pair of opposed sides 114 b, 114 d. Theside 114 a is disposed generally parallel to the side 114 c, while theside 114 b is disposed generally parallel to the side 114 d. Each of thesides 114 a, 114 b, 114 c, 114 d is disposed generally perpendicular tothe planar top and bottom surfaces of the body portion 114. Also, eachof the first pair of opposed sides 114 a, 114 c is disposed generallyperpendicular to each of the second pair of opposed sides 114 b, 114 d.In addition, as shown in FIG. 10, each of the opposed sides 114 a, 114 ccomprises a beam connecting portion 128 extending outward therefrom. Inthe illustrated embodiment, it can be seen that each of the beamconnecting portions 128 comprises a plurality of apertures 130 (e.g.,two apertures 130) disposed therethrough for accommodating fasteners(e.g., screws) that attach the load transducer 100 to another object,such as a robotic arm, etc. Also, as depicted in the side views of FIGS.11 and 12 and the bottom view of FIG. 14, the bottom surface of thecentral body portion 114 comprises a raised portion or standoff portion126 for elevating the transducer beams 116, 118, 120, 122 above theobject (e.g., robotic arm) to which the load transducer 100 is attachedso that forces and/or moments are capable of being accurately measuredby the load transducer 100. In one or more embodiments, the structuralcomponents to which the load transducer 100 is mounted are connectedonly to the top standoff portions 124 and the bottom standoff 126 so asto ensure that the total load applied to the load transducer 100 istransmitted through the transducer beams 116, 118, 120, 122.

As shown in FIGS. 10-14, the illustrated generally U-shaped transducerbeams 116, 118, 120, 122 are each attached to one of the sides 114 a,114 b, 114 c, 114 d of the body portion 114 via a connecting portion128, and extend generally horizontally outward therefrom. In particular,beams 116, 118 extend generally horizontally outward from opposed sidesof the beam connecting portion 128 attached to side 114 a of the bodyportion 114, while the beams 120, 122 extend generally horizontallyoutward from opposed sides of the beam connecting portion 128 attachedto side 114 c of the body portion 114. As best shown in FIG. 10, the topand bottom surfaces of each of the illustrated beams 116, 118, 120, 122are disposed substantially co-planar with the top and bottom surfaces ofthe body portion 114. Each of the illustrated beams 116, 118, 120, 122has a U-shaped cantilevered end relative to the body portion 114 thatallows for deflection of the ends of the beams in multiple directions.

With particular reference to FIGS. 10, 13, and 14, it can be seen thateach of the generally U-shaped beams 116, 118, 120, 122 comprises aplurality of segmental beam portions, wherein each of the successivebeam portions are disposed substantially perpendicular to theimmediately preceding beam portion. For example, as shown in FIG. 10,the first generally U-shaped transducer beam 116 comprises a first beamportion 116 a extending from a first side of the beam connecting portion128, a second beam portion 116 b connected to the first beam portion 116a and disposed substantially perpendicular thereto, a third beam portion116 c connected to the second beam portion 116 b and disposedsubstantially perpendicular thereto, and a fourth beam portion 116 dconnected to the third beam portion 116 c and disposed substantiallyperpendicular thereto. Similarly, the second generally U-shapedtransducer beam 118 comprises a first beam portion 118 a extending froma second side of the beam connecting portion 128 (which is generallyopposite to the first side of the beam connecting portion 128 from whichthe first beam portion 116 a extends), a second beam portion 118 bconnected to the first beam portion 118 a and disposed substantiallyperpendicular thereto, a third beam portion 118 c connected to thesecond beam portion 118 b and disposed substantially perpendicularthereto, and a fourth beam portion 118 d connected to the third beamportion 118 c and disposed substantially perpendicular thereto. Withreference to FIGS. 10, 13, and 14, it can be seen that the generallyU-shaped transducer beams 120, 122 are generally mirror images of thegenerally U-shaped transducer beams 116, 118, and thus, have the samestructure as the generally U-shaped transducer beams 116, 118. Referringagain to FIGS. 10, 13, and 14, it can be seen that the fourth beamportion of each of the generally U-shaped transducer beams 116, 118,120, 122 comprises a raised portion or standoff portion 124 withmounting apertures 132 (e.g., two apertures 132) disposed therethroughfor accommodating fasteners (e.g., screws) that attach the loadtransducer 100 to another object, such as a robotic arm, etc. Inaddition, as shown in FIGS. 10 and 13, each generally U-shapedtransducer beam 116, 118, 120, 122 comprises a central beam gap 106,which is bounded by the second, third, and fourth beam portions. Also,it can be seen that the first and second beam portions of eachtransducer beam 116, 118, 120, 122 are separated from the opposing sidesof the central body portion 114 by an L-shaped gap 104. That is, thesides of the central body portion 114, which face the sides of the firstand second beam portions in an opposing relationship, are separated fromthe sides of the first and second beam portions by the L-shaped gap 104.

As best shown in the perspective view of FIG. 10, the illustrated loadcells are located on the transducer beams 116, 118, 120, 122. In theillustrated embodiment, each load cell comprises a plurality of straingages 134, 136, 138. Specifically, in the illustrated embodiment, eachof the first portions (e.g., 116 a, 118 a) of the transducer beams 116,118, 120, 122 comprise a strain gage 134 disposed on the top surfacethereof that is sensitive to the vertical force component (i.e., a F_(Z)strain gage). The first portions (e.g., 116 a, 118 a) of the transducerbeams 116, 118, 120, 122 also each comprise a strain gage 138 disposedon a side surface thereof that is sensitive to a first shear forcecomponent (i.e., a F_(Y) strain gage). Also, in the illustratedembodiment, each of the fourth portions (e.g., 116 d, 118 d) of thetransducer beams 116, 118, 120, 122 comprise a strain gage 136 disposedon a side surface thereof that is sensitive to a second shear forcecomponent (i.e., a F_(X) strain gage).

As best shown in FIG. 10, the illustrated load cells are configured asbending beam load cells. The illustrated strain gages 134, 136, 138 aremounted to either top or side surfaces of the beams 116, 118, 120, 122between their attachment locations to the beam connecting portions 128and the raised end portions 124 thereof. Alternatively, the strain gages134 can be mounted to the bottom surfaces of the first beam portions(e.g., 116 a, 118 a) of the transducer beams 116, 118, 120, 122, whilethe strain gages 138 can be mounted to the opposite side surfaces of thefirst beam portions (e.g., 116 a, 118 a) of the transducer beams 116,118, 120, 122. Similarly, the strain gages 136 can be mounted to theopposite side surfaces of the fourth beam portions (e.g., 116 d, 118 d)of the transducer beams 116, 118, 120, 122. In general, the strain gages134, 136, 138 are mounted to surfaces generally normal to the directionof applied vertical and/or shear forces (i.e., F_(X), F_(Y), F_(Z)). Itis also noted that alternatively, the strain gages 134 can be mounted atboth the top surface and the bottom surface of the first beam portionsof the beams 116, 118, 120, 122, the strain gages 138 can be mounted atboth opposed side surfaces of first beam portions of the beams 116, 118,120, 122, and/or the strain gages 136 can be mounted at both opposedside surfaces of the beams 116, 118, 120, 122. These strain gages 134,136, 138 measure force either by bending moment or difference of bendingmoments at two cross sections. As force is applied to the ends of thebeams, the beams 116, 118, 120, 122 bend. This bending either stretchesor compresses the strain gages 134, 136, 138, which in turn changes theresistance of the electrical current passing therethrough. The amount ofchange in the electrical voltage or current is proportional to themagnitude of the applied force, as applied to the ends of respectivebeams 116, 118, 120, 122.

Next, referring to FIGS. 15-18, a load transducer 200 according to afourth exemplary embodiment of the present invention will be described.Referring initially to the perspective view of FIG. 15, it can be seenthat the load transducer 200 generally includes a one-piece compacttransducer frame 204 that is generally in the form of square band-shapedelement with a central opening 202 disposed therethrough. As bestillustrated in FIGS. 15 and 18, the square band-shaped transducer frame204 comprises a first transducer beam side portion 206, a secondtransducer beam side portion 208, a third transducer beam side portion210, and a fourth transducer beam side portion 212. Also, as shown inFIG. 15, the transducer beam side portions 206, 208, 210, 212 comprise aplurality of load cells or transducer elements for measuring forcesand/or moments. The transducer frame 204 of the load transducer 200 issimilar to the other transducers (e.g., transducers 300, 400) that willbe described hereinafter, except that the central body portion of thesetransducers (e.g., 300, 400) has been removed in the load transducer200.

As shown in FIGS. 15-18, the illustrated transducer beam side portions206, 208, 210, 212 of the transducer frame 204 are arranged in agenerally square configuration. In particular, with reference to FIGS.15 and 18, the first transducer beam side portion 206 is connected tothe second transducer beam side portion 208 on one of its longitudinalends, and the fourth transducer beam side portion 212 on the other oneof its longitudinal ends, and the first transducer beam side portion 206is disposed generally perpendicular to each of the second and fourthtransducer beam side portions 208, 212. The second transducer beam sideportion 208 is connected to the first transducer beam side portion 206on one of its longitudinal ends, and the third transducer beam sideportion 210 on the other one of its longitudinal ends, and the secondtransducer beam side portion 208 is disposed generally perpendicular toeach of the first and third transducer beam side portions 206, 210. Thethird transducer beam side portion 210 is connected to the secondtransducer beam side portion 208 on one of its longitudinal ends, andthe fourth transducer beam side portion 212 on the other one of itslongitudinal ends, and the third transducer beam side portion 210 isdisposed generally perpendicular to each of the second and fourthtransducer beam side portions 208, 212. The fourth transducer beam sideportion 212 is connected to the third transducer beam side portion 210on one of its longitudinal ends, and the first transducer beam sideportion 206 on the other one of its longitudinal ends, and the fourthtransducer beam side portion 212 is disposed generally perpendicular toeach of the first and third transducer beam side portions 206, 210.Referring to FIGS. 15, 17, and 18, it can be seen that the top surfaceof the second transducer beam side portion 208 and the top surface ofthe fourth transducer beam side portion 212 each comprises a centralraised portion or standoff portion 214 with spaced apart mountingapertures 218 (e.g., two spaced apart apertures 218) disposedtherethrough for accommodating fasteners (e.g., screws) that attach theload transducer 200 to another object, such as a robotic arm, etc.Similarly, with reference to FIGS. 15 and 16, it can be seen that thebottom surface of the first transducer beam side portion 206 and thebottom surface of the third transducer beam side portion 210 eachcomprises a central raised portion or standoff portion 216 with spacedapart mounting apertures 218 (e.g., two spaced apart apertures 218)disposed therethrough for accommodating fasteners (e.g., screws) thatattach the load transducer 200 to another object, such as a robotic arm,etc.

As best shown in the perspective view of FIG. 15, the illustrated loadcells are located on the transducer beam side portions 206, 208, 210,212. In the illustrated embodiment, each load cell comprises one or morestrain gages 220, 222, 224. Specifically, in the illustrated embodiment,the first transducer beam side portion 206 and the third transducer beamside portion 210 each comprise a plurality of spaced apart strain gages220 (e.g., two spaced apart strain gages 220) disposed on the topsurface thereof that is sensitive to the vertical force component (i.e.,a F_(Z) strain gage). The second transducer beam side portion 208 andthe fourth transducer beam side portion 212 also each comprise aplurality of spaced apart strain gages 222 (e.g., two spaced apartstrain gages 222) disposed on a side surface thereof that is sensitiveto a first shear force component (i.e., a F_(X) strain gage). Also, inthe illustrated embodiment, the first transducer beam side portion 206and the third transducer beam side portion 210 also each comprise aplurality of spaced apart strain gages 224 (e.g., two spaced apartstrain gages 224) disposed on a side surface thereof that is sensitiveto a second shear force component (i.e., a F_(Y) strain gage).

As best shown in FIG. 15, the illustrated load cells are configured asbending beam load cells. The illustrated strain gages 220, 222, 224 aremounted to either top or side surfaces of the transducer beam sideportions 206, 208, 210, 212 between the opposed longitudinal endsthereof. Alternatively, the strain gages 220 can be mounted to thebottom surfaces of the first and third transducer beam side portions206, 210, while the strain gages 222 can be mounted to the opposite sidesurfaces of the second and fourth transducer beam side portions 208,212. Similarly, the strain gages 224 can be mounted to the opposite sidesurfaces of the first and third transducer beam side portions 206, 210.In general, the strain gages 220, 222, 224 are mounted to surfacesgenerally normal to the direction of applied vertical and/or shearforces (i.e., F_(X), F_(Y), F_(Z)). It is also noted that alternatively,the strain gages 220 can be mounted at both the top surface and thebottom surface of the first and third transducer beam side portions 206,210, the strain gages 222 can be mounted at both opposed side surfacesof second and fourth transducer beam side portions 208, 212, and/or thestrain gages 224 can be mounted at both opposed side surfaces of thefirst and third transducer beam side portions 206, 210. These straingages 220, 222, 224 measure force either by bending moment or differenceof bending moments at two cross sections. As force is applied to thebeams, the beams 206, 208, 210, 212 bend. This bending either stretchesor compresses the strain gages 220, 222, 224, which in turn changes theresistance of the electrical current passing therethrough. The amount ofchange in the electrical voltage or current is proportional to themagnitude of the applied force, as transferred through the end portionsof respective beams 206, 208, 210, 212.

An exemplary mounting arrangement for the load transducer 200 isillustrated in FIG. 25. As depicted in the perspective view of FIG. 25,the load transducer 200 is mounted between a top plate member 226 and abottom plate member 228. Specifically, in this mounting arrangement, thebottom surface 226 a of the top plate member 226 abuts the top surfacesof the standoff portions 214 on the second and fourth transducer beamside portions 208, 212, while the top surface 228 a of the bottom platemember 228 abuts the bottom surfaces of the standoff portions 216 on thefirst and third transducer beam side portions 206, 210. As such, in thismounting arrangement, an upper gap 230 is formed between the topsurfaces of the load transducer 200 and the bottom surface 226 a of thetop plate member 226 by the two spaced apart top standoff portions 214.Similarly, a lower gap 232 is formed between the bottom surfaces of theload transducer 200 and the top surface 228 a of the bottom plate member228 by the two spaced apart bottom standoff portions 216. Thus, asresult of the mounting arrangement illustrated in FIG. 25, the entireload exerted on the load transducer 200 by the top and bottom platemembers 226, 228 is transferred through the corner portions of thetransducer frame 204, which are instrumented with the strain gages 220,222, 224 and are spaced apart from the top and bottom plate members 226,228 by the standoff portions 214, 216.

While the exemplary mounting arrangement is illustrated in FIG. 25 usingthe load transducer 200, it is to be understood that each of the otherload transducers 10, 10′, 100, 300, 400, 500, 600, 700, 800 describedherein are mounted in generally the same manner to adjoining structures(e.g., plate members 226, 228 or components of a robotic arm). That is,the standoff portions described on the load transducers 10, 10′, 100,300, 400, 500, 600, 700, 800 perform the same functions as thosedescribed in conjunction with the load transducer 200 above. Inparticular, the adjoining structures to which the transducers aremounted are only connected to the top standoff portions and the bottomstandoff portions of each load transducer 10, 10′, 100, 300, 400, 500,600, 700, 800 so as to ensure that the total loads applied to the loadtransducers 10, 10′, 100, 300, 400, 500, 600, 700, 800 are transmittedthrough the instrumented portions of the transducer beams of thetransducers.

FIG. 19 illustrates a load transducer 300 according to a fifth exemplaryembodiment of the present invention. With reference to this figure, itcan be seen that, in some respects, the fifth exemplary embodiment issimilar to that of the fourth embodiment. Moreover, some parts arecommon to both such embodiments. For the sake of brevity, the parts thatthe fifth embodiment of the load transducer has in common with thefourth embodiment will only be briefly mentioned because thesecomponents have already been explained in detail above.

Initially, referring to the perspective view of FIG. 19, it can be seenthat, unlike the fourth exemplary embodiment of the load transducer, theload transducer 300 comprises a central body portion 302. Also, unlikethe load transducer 200 of the fourth embodiment, the second and fourthtransducer beam side portions 308, 312 have side projecting portions 326extending from the inner sides thereof towards the central body portion302. As shown in FIG. 19, the load transducer 300 generally includes aone-piece compact transducer frame 304 with a central body portion 302and a plurality of transducer beam side portions 306, 308, 310, 312.

With reference again to FIG. 19, it can be seen that the illustratedcentral body portion 302 is generally in the form of rectangularband-shaped element with a central opening 303 disposed therethrough. InFIG. 19, it can be seen that the body portion 302 comprises a first pairof opposed side portions 302 a, 302 c and a second pair of opposed sideportions 302 b, 302 d. The side portion 302 a is disposed generallyparallel to the side portion 302 c, while the side portion 302 b isdisposed generally parallel to the side portion 302 d. Each of the sidesurfaces of the side portions 302 a, 302 b, 302 c, 302 d is disposedgenerally perpendicular to the planar top and bottom surfaces thereof.Also, each of the first pair of opposed side portions 302 a, 302 c isdisposed generally perpendicular to each of the second pair of opposedsides portions 302 b, 302 d. In addition, as shown in FIG. 19, each ofthe opposed side portions 302 a, 302 c forms a middle portion of thefirst and third transducer beam side portions 306, 310. In theillustrated embodiment, it can be seen that each of the opposed sideportions 302 a, 302 c comprises a plurality of apertures 318 (e.g., twoapertures 318) disposed therethrough for accommodating fasteners (e.g.,screws) that attach the load transducer 300 to another object, such as arobotic arm, etc. Also, as depicted in the FIG. 19, the central bodyportion 302 comprises a raised top portion or top standoff portion 314for spacing the transducer beam side portions 306, 308, 310, 312 apartfrom the object (e.g., robotic arm) to which the load transducer 300 isattached so that forces and/or moments are capable of being accuratelymeasured by the load transducer 300.

As shown in FIG. 19, the illustrated transducer beam side portions 306,308, 310, 312 of the transducer frame 304 are arranged in a generallysquare configuration. In particular, with reference to FIG. 19, thefirst transducer beam side portion 306 is connected to the secondtransducer beam side portion 308 on one of its longitudinal ends, andthe fourth transducer beam side portion 312 on the other one of itslongitudinal ends, and the first transducer beam side portion 306 isdisposed generally perpendicular to each of the second and fourthtransducer beam side portions 308, 312. The second transducer beam sideportion 308 is connected to the first transducer beam side portion 306on one of its longitudinal ends, and the third transducer beam sideportion 310 on the other one of its longitudinal ends, and the secondtransducer beam side portion 308 is disposed generally perpendicular toeach of the first and third transducer beam side portions 306, 310. Thethird transducer beam side portion 310 is connected to the secondtransducer beam side portion 308 on one of its longitudinal ends, andthe fourth transducer beam side portion 312 on the other one of itslongitudinal ends, and the third transducer beam side portion 310 isdisposed generally perpendicular to each of the second and fourthtransducer beam side portions 308, 312. The fourth transducer beam sideportion 312 is connected to the third transducer beam side portion 310on one of its longitudinal ends, and the first transducer beam sideportion 306 on the other one of its longitudinal ends, and the fourthtransducer beam side portion 312 is disposed generally perpendicular toeach of the first and third transducer beam side portions 306, 310.Referring to FIG. 19, it can be seen that the bottom surface of thesecond transducer beam side portion 308 and the bottom surface of thefourth transducer beam side portion 312 each comprises a centralstandoff portion 316, which is connected to the side projecting portion326 on each of the transducer beam side portions 308, 312. The sideprojecting portions 326 each comprise spaced apart mounting apertures328 (e.g., two spaced apart apertures 328) disposed therethrough foraccommodating fasteners (e.g., screws) that attach the load transducer300 to another object, such as a robotic arm, etc.

As best shown in the perspective view of FIG. 19, the illustrated loadcells are located on the transducer beam side portions 306, 308, 310,312. In the illustrated embodiment, each load cell comprises one or morestrain gages 320, 322, 324. Specifically, in the illustrated embodiment,the second transducer beam side portion 308 and the fourth transducerbeam side portion 312 each comprise a plurality of spaced apart straingages 320 (e.g., two spaced apart strain gages 320) disposed on the topsurface thereof that is sensitive to the vertical force component (i.e.,a F_(Z) strain gage). The second transducer beam side portion 308 andfourth transducer beam side portion 312 also each comprise a pluralityof spaced apart strain gages 322 (e.g., two spaced apart strain gages322) disposed on a side surface thereof that is sensitive to a firstshear force component (i.e., a F_(X) strain gage). Also, in theillustrated embodiment, the first transducer beam side portion 306 andthe third transducer beam side portion 310 also each comprise aplurality of spaced apart strain gages 324 (e.g., two spaced apartstrain gages 324) disposed on a side surface thereof that is sensitiveto a second shear force component (i.e., a F_(Y) strain gage).

FIG. 20 illustrates a load transducer 400 according to a sixth exemplaryembodiment of the present invention. With reference to this figure, itcan be seen that, in some respects, the sixth exemplary embodiment issimilar to that of the fifth embodiment. Moreover, some parts are commonto both such embodiments. For the sake of brevity, the parts that thesixth embodiment of the load transducer has in common with the fifthembodiment will only be briefly mentioned because these components havealready been explained in detail above.

Initially, referring to the perspective view of FIG. 20, it can be seenthat, unlike the fifth exemplary embodiment of the load transducer, allfour sides of the central body portion 402 of the load transducer 400are spaced apart from the transducer beam side portions 406, 408, 410,412. In particular, the central body portion 402 is spaced apart fromthe transducer beam side portions 406, 408, 410, 412 by the two C-shapedgaps 426. Also, unlike the load transducer 300 of the fifth embodiment,the first and third transducer beam side portions 406, 410 of the loadtransducer 400 are connected to the central body portion 402 by the beamconnecting portions 417. Although, like the load transducer 300, theload transducer 400 generally includes a one-piece compact transducerframe 404 with a central body portion 402 and a plurality of transducerbeam side portions 406, 408, 410, 412.

With reference again to FIG. 20, it can be seen that the illustratedcentral body portion 402 is generally in the form of rectangularband-shaped element with a central opening 403 disposed therethrough. InFIG. 20, it can be seen that the body portion 402 comprises a first pairof opposed side portions 402 a, 402 c and a second pair of opposed sideportions 402 b, 402 d. The side portion 402 a is disposed generallyparallel to the side portion 402 c, while the side portion 402 b isdisposed generally parallel to the side portion 402 d. Each of the sidesurfaces of the side portions 402 a, 402 b, 402 c, 402 d is disposedgenerally perpendicular to the planar top and bottom surfaces thereof.Also, each of the first pair of opposed side portions 402 a, 402 c isdisposed generally perpendicular to each of the second pair of opposedsides portions 402 b, 402 d. In addition, as shown in FIG. 20, each ofthe opposed side portions 402 a, 402 c is connected to the first andthird transducer beam side portions 406, 410 by beam connecting portions417. In the illustrated embodiment, it can be seen that each of the beamconnecting portions 417 comprises a plurality of apertures 418 (e.g.,two apertures 418) disposed therethrough for accommodating fasteners(e.g., screws) that attach the load transducer 400 to another object,such as a robotic arm, etc.

As shown in FIG. 20, the illustrated transducer beam side portions 406,408, 410, 412 of the transducer frame 404 are arranged in a generallysquare configuration. In particular, with reference to FIG. 20, thefirst transducer beam side portion 406 is connected to the secondtransducer beam side portion 408 on one of its longitudinal ends, andthe fourth transducer beam side portion 412 on the other one of itslongitudinal ends, and the first transducer beam side portion 406 isdisposed generally perpendicular to each of the second and fourthtransducer beam side portions 408, 412. The second transducer beam sideportion 408 is connected to the first transducer beam side portion 406on one of its longitudinal ends, and the third transducer beam sideportion 410 on the other one of its longitudinal ends, and the secondtransducer beam side portion 408 is disposed generally perpendicular toeach of the first and third transducer beam side portions 406, 410. Thethird transducer beam side portion 410 is connected to the secondtransducer beam side portion 408 on one of its longitudinal ends, andthe fourth transducer beam side portion 412 on the other one of itslongitudinal ends, and the third transducer beam side portion 410 isdisposed generally perpendicular to each of the second and fourthtransducer beam side portions 408, 412. The fourth transducer beam sideportion 412 is connected to the third transducer beam side portion 410on one of its longitudinal ends, and the first transducer beam sideportion 406 on the other one of its longitudinal ends, and the fourthtransducer beam side portion 412 is disposed generally perpendicular toeach of the first and third transducer beam side portions 406, 410.Referring to FIG. 20, it can be seen that the top surface of the secondtransducer beam side portion 408 and the top surface of the fourthtransducer beam side portion 412 each comprises a central raised portionor standoff portion 414 with spaced apart mounting apertures 428 (e.g.,two spaced apart apertures 428) disposed therethrough for accommodatingfasteners (e.g., screws) that attach the load transducer 400 to anotherobject, such as a robotic arm, etc. Similarly, with reference to FIG.20, it can be seen that the bottom surface of the first transducer beamside portion 406 and the bottom surface of the third transducer beamside portion 410 each comprises a central raised portion or standoffportion 416.

As best shown in the perspective view of FIG. 20, the illustrated loadcells are located on the transducer beam side portions 406, 408, 410,412. In the illustrated embodiment, each load cell comprises one or morestrain gages 420, 422, 424. Specifically, in the illustrated embodiment,the first transducer beam side portion 406 and the third transducer beamside portion 410 each comprise a plurality of spaced apart strain gages420 (e.g., two spaced apart strain gages 420) disposed on the topsurface thereof that is sensitive to the vertical force component (i.e.,a F_(Z) strain gage). The second transducer beam side portion 408 andfourth transducer beam side portion 412 also each comprise a pluralityof spaced apart strain gages 422 (e.g., two spaced apart strain gages422) disposed on a side surface thereof that is sensitive to a firstshear force component (i.e., a F_(X) strain gage). Also, in theillustrated embodiment, the first transducer beam side portion 406 andthe third transducer beam side portion 410 also each comprise aplurality of spaced apart strain gages 424 (e.g., two spaced apartstrain gages 424) disposed on a side surface thereof that is sensitiveto a second shear force component (i.e., a F_(Y) strain gage).

FIG. 21 illustrates a load transducer 500 according to a seventhexemplary embodiment of the present invention. With reference to thisfigure, it can be seen that, in some respects, the seventh exemplaryembodiment is similar to that of the fifth embodiment. Moreover, someparts are common to both such embodiments. For the sake of brevity, theparts that the seventh embodiment of the load transducer has in commonwith the fifth embodiment will only be briefly mentioned because thesecomponents have already been explained in detail above.

Initially, referring to the perspective view of FIG. 21, it can be seenthat, like the fifth embodiment described above, the load transducer 500generally includes a one-piece compact transducer frame 504 with acentral body portion 502 and a plurality of transducer beam sideportions 506, 508, 510, 512, 514, 516. Although, the central bodyportion 502 of the load transducer 500 is considerably wider than thecentral body portion 302 of the load transducer 300.

With reference again to FIG. 21, it can be seen that the illustratedcentral body portion 502 is generally in the form of square band-shapedelement with a central opening 530 disposed therethrough. In FIG. 21, itcan be seen that the body portion 502 comprises a first pair of opposedside portions 502 a, 502 c and a second pair of opposed side portions502 b, 502 d. The side portion 502 a is disposed generally parallel tothe side portion 502 c, while the side portion 502 b is disposedgenerally parallel to the side portion 502 d. Each of the side surfacesof the side portions 502 a, 502 b, 502 c, 502 d is disposed generallyperpendicular to the planar top and bottom surfaces thereof. Also, eachof the first pair of opposed side portions 502 a, 502 c is disposedgenerally perpendicular to each of the second pair of opposed sidesportions 502 b, 502 d. In addition, as shown in FIG. 21, each of theopposed side portions 502 a, 502 c is disposed between a respective pairof transducer beam side portions 506, 508 and 512, 514. In theillustrated embodiment, it can be seen that each of the opposed sideportions 502 a, 502 c comprises a plurality of apertures 532 (e.g., twoapertures 532) disposed therethrough for accommodating fasteners (e.g.,screws) that attach the load transducer 500 to another object, such as arobotic arm, etc. Also, as depicted in the FIG. 21, the central bodyportion 502 comprises a raised bottom portion or bottom standoff portion520 for spacing the transducer beam side portions 506, 508, 510, 512,514, 516 apart from the object (e.g., robotic arm) to which the loadtransducer 500 is attached so that forces and/or moments are capable ofbeing accurately measured by the load transducer 500.

As shown in FIG. 21, the first set of illustrated transducer beam sideportions 506, 514, 516 of the transducer frame 504 are arranged in agenerally C-shaped configuration on a first side of the central bodyportion 502. A first side aperture 534 is formed between the sideportion 502 d of the central body portion 502 and the first set oftransducer beam side portions 506, 514, 516. Referring again to FIG. 21,it can be seen that the first transducer beam side portion 506 isconnected to the sixth transducer beam side portion 516 on one of itslongitudinal ends, and the side portion 502 d of the central bodyportion 502 on the other one of its longitudinal ends, and the firsttransducer beam side portion 506 is disposed generally perpendicular tothe side portion 502 d of the central body portion 502 and to sixthtransducer beam side portion 516. Similarly, the fifth transducer beamside portion 514 is connected to the sixth transducer beam side portion516 on one of its longitudinal ends, and the side portion 502 d of thecentral body portion 502 on the other one of its longitudinal ends, andthe fifth transducer beam side portion 514 is disposed generallyperpendicular to the side portion 502 d of the central body portion 502and to sixth transducer beam side portion 516. The sixth transducer beamside portion 516 is connected to the first transducer beam side portion506 on one of its longitudinal ends, and the fifth transducer beam sideportion 514 on the other one of its longitudinal ends, and the sixthtransducer beam side portion 516 is disposed generally perpendicular toeach of the first and fifth transducer beam side portions 506, 514.Turning again to FIG. 21, it can be seen that the second set oftransducer beam side portions 508, 510, 512 of the transducer frame 504is arranged in a generally C-shaped configuration on a second side ofthe central body portion 502, which is opposite to the first side of thecentral body portion 502. A second side aperture 534 is formed betweenthe side portion 502 b of the central body portion 502 and the secondset of transducer beam side portions 508, 510, 512. In FIG. 21, it canbe seen that the second transducer beam side portion 508 is connected tothe third transducer beam side portion 510 on one of its longitudinalends, and the side portion 502 b of the central body portion 502 on theother one of its longitudinal ends, and the second transducer beam sideportion 508 is disposed generally perpendicular to the side portion 502b of the central body portion 502 and to third transducer beam sideportion 510. Similarly, the fourth transducer beam side portion 512 isconnected to the third transducer beam side portion 510 on one of itslongitudinal ends, and the side portion 502 b of the central bodyportion 502 on the other one of its longitudinal ends, and the fourthtransducer beam side portion 512 is disposed generally perpendicular tothe side portion 502 b of the central body portion 502 and to thirdtransducer beam side portion 510. The third transducer beam side portion510 is connected to the second transducer beam side portion 508 on oneof its longitudinal ends, and the fourth transducer beam side portion512 on the other one of its longitudinal ends, and the third transducerbeam side portion 510 is disposed generally perpendicular to each of thesecond and fourth transducer beam side portions 508, 512. Also, as shownin FIG. 21, it can be seen that the top surface of the third transducerbeam side portion 510 and the top surface of the sixth transducer beamside portion 516 each comprises a central standoff portion 518. Thecentral standoff portions 518 each comprise spaced apart mountingapertures 522 (e.g., two spaced apart apertures 522) disposedtherethrough for accommodating fasteners (e.g., screws) that attach theload transducer 500 to another object, such as a robotic arm, etc.

As best shown in the perspective view of FIG. 21, the illustrated loadcells are located on the transducer beam side portions 506, 508, 510,512, 514, 516. In the illustrated embodiment, each load cell comprisesone or more strain gages 524, 526, 528. Specifically, in the illustratedembodiment, the first transducer beam side portion 506, the secondtransducer beam side portion 508, the fourth transducer beam sideportion 512, and the fifth transducer beam side portion 514 eachcomprise a strain gage 524 disposed on the top surface thereof that issensitive to the vertical force component (i.e., a F_(Z) strain gage).The third transducer beam side portion 510 and the sixth transducer beamside portion 516 also each comprise a plurality of spaced apart straingages 526 (e.g., two spaced apart strain gages 526) disposed on a sidesurface thereof that is sensitive to a first shear force component(i.e., a F_(X) strain gage). Also, in the illustrated embodiment, thefirst transducer beam side portion 506, the second transducer beam sideportion 508, the fourth transducer beam side portion 512, and the fifthtransducer beam side portion 514 each comprises a strain gage 528disposed on an outer side surface thereof that is sensitive to a secondshear force component (i.e., a F_(Y) strain gage).

FIG. 22 illustrates a load transducer 600 according to an eighthexemplary embodiment of the present invention. With reference to thisfigure, it can be seen that, in some respects, the eighth exemplaryembodiment is similar to that of the preceding embodiments. Moreover,some parts are common to all of the embodiments. For the sake ofbrevity, the parts that the eighth embodiment of the load transducer hasin common with the preceding embodiments will only be briefly mentionedbecause these components have already been explained in detail above.

Initially, referring to the perspective view of FIG. 22, it can be seenthat, like the preceding embodiments described above, the loadtransducer 600 generally includes a one-piece compact transducer frame604 with a central body portion 602 and a plurality of transducer beams606, 608, 610, 612, 614, 616 connected thereto. Although, the transducerbeams 606, 608, 610, 612, 614, 616 are arranged in a differentconfiguration than that which was described for the precedingembodiments.

With reference again to FIG. 22, it can be seen that the illustratedcentral body portion 602 is generally in the form of square band-shapedelement with a central opening 630 disposed therethrough. In FIG. 22, itcan be seen that the body portion 602 comprises a first pair of opposedside portions 602 a, 602 c and a second pair of opposed side portions602 b, 602 d. The side portion 602 a is disposed generally parallel tothe side portion 602 c, while the side portion 602 b is disposedgenerally parallel to the side portion 602 d. Each of the side surfacesof the side portions 602 a, 602 b, 602 c, 602 d is disposed generallyperpendicular to the planar top and bottom surfaces thereof. Also, eachof the first pair of opposed side portions 602 a, 602 c is disposedgenerally perpendicular to each of the second pair of opposed sidesportions 602 b, 602 d. In addition, as shown in FIG. 22, each of theopposed side portions 602 b, 602 d is connected to a respective set oftransducer beams 606, 608, 610 and 612, 614, 616. In the illustratedembodiment, it can be seen that each of the opposed side portions 602 a,602 c comprises a plurality of apertures 632 (e.g., two apertures 632)disposed therethrough for accommodating fasteners (e.g., screws) thatattach the load transducer 600 to another object, such as a robotic arm,etc.

As shown in FIG. 22, the first set of illustrated transducer beams 606,608, 610 of the transducer frame 604 is arranged in a generally T-shapedconfiguration on a first side of the central body portion 602. A firstside aperture 634 is formed between the side portion 602 d of thecentral body portion 602 and the first set of transducer beam sideportions 606, 608, 610. Referring again to FIG. 22, it can be seen thatthe first transducer beam 606 is connected to the side portion 602 d ofthe central body portion 602 by means of two spaced apart connectingtransducer beams 608, 610. Specifically, the second transducer beam 608is connected to an inner side of the first transducer beam 606 on one ofits longitudinal ends, and the side portion 602 d of the central bodyportion 602 on the other one of its longitudinal ends, and the secondtransducer beam 608 is disposed generally perpendicular to the sideportion 602 d of the central body portion 602 and to first transducerbeam 606. Similarly, the third transducer beam 610 is connected to theinner side of the first transducer beam 606 on one of its longitudinalends, and the side portion 602 d of the central body portion 602 on theother one of its longitudinal ends, and the third transducer beam 610 isdisposed generally perpendicular to the side portion 602 d of thecentral body portion 602 and to first transducer beam 606. Turning againto FIG. 22, it can be seen that the second set of transducer beams 612,614, 616 of the transducer frame 604 is arranged in a generally T-shapedconfiguration on a second side of the central body portion 602, which isopposite to the first side of the central body portion 602. A secondside aperture 634 is formed between the side portion 602 b of thecentral body portion 602 and the second set of transducer beam sideportions 612, 614, 616. In FIG. 22, similar to the first transducer beam606, it can be seen that the fourth transducer beam 612 is connected tothe side portion 602 b of the central body portion 602 by means of twospaced apart connecting transducer beams 614, 616. Specifically, thefifth transducer beam 614 is connected to an inner side of the fourthtransducer beam 612 on one of its longitudinal ends, and the sideportion 602 b of the central body portion 602 on the other one of itslongitudinal ends, and the fifth transducer beam 614 is disposedgenerally perpendicular to the side portion 602 b of the central bodyportion 602 and to fourth transducer beam 612. Similarly, the sixthtransducer beam 616 is connected to the inner side of the fourthtransducer beam 612 on one of its longitudinal ends, and the sideportion 602 b of the central body portion 602 on the other one of itslongitudinal ends, and the sixth transducer beam 616 is disposedgenerally perpendicular to the side portion 602 b of the central bodyportion 602 and to fourth transducer beam 612. Also, as shown in FIG.22, it can be seen that the bottom surface of the first transducer beam606 and the bottom surface of the fourth transducer beam 612 eachcomprises a central standoff portion 620. In addition, it can be seenthat the opposed longitudinal ends of the first transducer beam 606 andthe fourth transducer beam 612 are each provided with raised standoffportions 618. Each raised standoff portion 618 is provided with amounting aperture 622 disposed therethrough for accommodating arespective fastener (e.g., a screw) that attaches the load transducer600 to another object, such as a robotic arm, etc.

As best shown in the perspective view of FIG. 22, the illustrated loadcells are located on the transducer beams 606, 608, 610, 612, 614, 616.In the illustrated embodiment, each load cell comprises one or morestrain gages 624, 626, 628. Specifically, in the illustrated embodiment,the first transducer beam 606 and the fourth transducer beam 612 eachcomprise a pair of spaced apart strain gages 624 disposed on the topsurfaces thereof that are sensitive to the vertical force component(i.e., F_(Z) strain gages). In FIG. 22, it can be seen that each of thestrain gages 624 is disposed near the raised standoff portions 618 atthe opposed ends of the beams 606, 612. Also, in the illustratedembodiment, the second transducer beam 608, the third transducer beam610, the fifth transducer beam 614, and the sixth transducer beam 616each comprise a strain gage 626 disposed on an outer side surfacethereof that is sensitive to a first shear force component (i.e., aF_(X) strain gage). The first transducer beam 606 and the fourthtransducer beam 612 also each comprise a plurality of spaced apartstrain gages 628 (e.g., two spaced apart strain gages 628) disposed onan outer side surface thereof that is sensitive to a second shear forcecomponent (i.e., a F_(Y) strain gage).

FIG. 23 illustrates a load transducer 700 according to a ninth exemplaryembodiment of the present invention. With reference to this figure, itcan be seen that, in some respects, the ninth exemplary embodiment issimilar to that of the eighth embodiment. Moreover, some parts arecommon to all of the embodiments. For the sake of brevity, the partsthat the ninth embodiment of the load transducer has in common with theeighth embodiment will only be briefly mentioned because thesecomponents have already been explained in detail above.

Initially, referring to the perspective view of FIG. 23, it can be seenthat, like the eighth embodiment described above, the load transducer700 generally includes a one-piece compact transducer frame 704 with acentral body portion 702 and a plurality of transducer beams 706, 708,710, 712, 714, 716 connected thereto. Although, each of connectingtransducer beams 708, 710, and each of connecting transducer beams 714,716, are spaced considerably further apart from one another as comparedto the connecting transducer beams 608, 610, 614, 616 of the loadtransducer 600 such that the connecting beams 708, 710, 714, 716 aregenerally axially aligned with the side portions 702 a, 702 c of thecentral body portion 702.

With reference again to FIG. 23, it can be seen that the illustratedcentral body portion 702 is generally in the form of square band-shapedelement with a central opening 730 disposed therethrough. In FIG. 23, itcan be seen that the body portion 702 comprises a first pair of opposedside portions 702 a, 702 c and a second pair of opposed side portions702 b, 702 d. The side portion 702 a is disposed generally parallel tothe side portion 702 c, while the side portion 702 b is disposedgenerally parallel to the side portion 702 d. Each of the side surfacesof the side portions 702 a, 702 b, 702 c, 702 d is disposed generallyperpendicular to the planar top and bottom surfaces thereof. Also, eachof the first pair of opposed side portions 702 a, 702 c is disposedgenerally perpendicular to each of the second pair of opposed sidesportions 702 b, 702 d. In addition, as shown in FIG. 23, each of theopposed side portions 702 b, 702 d is connected to a respective set oftransducer beams 706, 708, 710 and 712, 714, 716. In the illustratedembodiment, it can be seen that each of the opposed side portions 702 a,702 c comprises a plurality of apertures 732 (e.g., two apertures 732)disposed therethrough for accommodating fasteners (e.g., screws) thatattach the load transducer 700 to another object, such as a robotic arm,etc. Also, as depicted in the FIG. 23, the central body portion 702comprises a raised bottom portion or bottom standoff portion 720 forspacing the transducer beams 706, 708, 710, 712, 714, 716 apart from anobject (e.g., robotic arm) to which the load transducer 700 is attachedso that forces and/or moments are capable of being accurately measuredby the load transducer 700.

As shown in FIG. 23, the first set of illustrated transducer beams 706,708, 710 of the transducer frame 704 is arranged in a generally T-shapedconfiguration on a first side of the central body portion 702 (with thewide base of the T-shaped arrangement being formed by the connectingbeam transducers 708, 710). A first side aperture 734 is formed betweenthe side portion 702 d of the central body portion 702 and the first setof transducer beam side portions 706, 708, 710. Referring again to FIG.23, it can be seen that the first transducer beam 706 is connected tothe side portion 702 d of the central body portion 702 by means of twospaced apart connecting transducer beams 708, 710. Specifically, thesecond transducer beam 708 is connected to an inner side of the firsttransducer beam 706 on one of its longitudinal ends, and the sideportion 702 d of the central body portion 702 on the other one of itslongitudinal ends, and the second transducer beam 708 is disposedgenerally perpendicular to the side portion 702 d of the central bodyportion 702 and to first transducer beam 706. Similarly, the thirdtransducer beam 710 is connected to the inner side of the firsttransducer beam 706 on one of its longitudinal ends, and the sideportion 702 d of the central body portion 702 on the other one of itslongitudinal ends, and the third transducer beam 710 is disposedgenerally perpendicular to the side portion 702 d of the central bodyportion 702 and to first transducer beam 706. Turning again to FIG. 23,it can be seen that the second set of transducer beams 712, 714, 716 ofthe transducer frame 704 is arranged in a generally T-shapedconfiguration on a second side of the central body portion 702, which isopposite to the first side of the central body portion 702 (with thewide base of the T-shaped arrangement being formed by the connectingbeam transducers 714, 716). A second side aperture 734 is formed betweenthe side portion 702 b of the central body portion 702 and the secondset of transducer beam side portions 712, 714, 716. In FIG. 23, similarto the first transducer beam 706, it can be seen that the fourthtransducer beam 712 is connected to the side portion 702 b of thecentral body portion 702 by means of two spaced apart connectingtransducer beams 714, 716. Specifically, the fifth transducer beam 714is connected to an inner side of the fourth transducer beam 712 on oneof its longitudinal ends, and the side portion 702 b of the central bodyportion 702 on the other one of its longitudinal ends, and the fifthtransducer beam 714 is disposed generally perpendicular to the sideportion 702 b of the central body portion 702 and to fourth transducerbeam 712. Similarly, the sixth transducer beam 716 is connected to theinner side of the fourth transducer beam 712 on one of its longitudinalends, and the side portion 702 b of the central body portion 702 on theother one of its longitudinal ends, and the sixth transducer beam 716 isdisposed generally perpendicular to the side portion 702 b of thecentral body portion 702 and to fourth transducer beam 712. Also, inFIG. 23, it can be seen that the opposed longitudinal ends of the firsttransducer beam 706 and the fourth transducer beam 712 are each providedwith raised standoff portions 718. Each raised standoff portion 718 isprovided with a mounting aperture 722 disposed therethrough foraccommodating a respective fastener (e.g., a screw) that attaches theload transducer 700 to another object, such as a robotic arm, etc.

As best shown in the perspective view of FIG. 23, the illustrated loadcells are located on the transducer beams 706, 708, 710, 712, 714, 716.In the illustrated embodiment, each load cell comprises one or morestrain gages 724, 726, 728. Specifically, in the illustrated embodiment,the first transducer beam 706 and the fourth transducer beam 712 eachcomprise a pair of spaced apart strain gages 724 disposed on the topsurfaces thereof that are sensitive to the vertical force component(i.e., F_(Z) strain gages). In FIG. 23, it can be seen that each of thestrain gages 724 is disposed near the raised standoff portions 718 atthe opposed ends of the beams 706, 712. Also, in the illustratedembodiment, the second transducer beam 708, the third transducer beam710, the fifth transducer beam 714, and the sixth transducer beam 716each comprise a strain gage 726 disposed on an outer side surfacethereof that is sensitive to a first shear force component (i.e., aF_(X) strain gage). The first transducer beam 706 and the fourthtransducer beam 712 also each comprise a plurality of spaced apartstrain gages 728 (e.g., two spaced apart strain gages 728) disposed onan outer side surface thereof that is sensitive to a second shear forcecomponent (i.e., a F_(Y) strain gage).

FIG. 24 illustrates a load transducer 800 according to a tenth exemplaryembodiment of the present invention. With reference to this figure, itcan be seen that, in some respects, the tenth exemplary embodiment issimilar to that of the preceding embodiments. Moreover, some parts arecommon to all of the embodiments. For the sake of brevity, the partsthat the tenth embodiment of the load transducer has in common with thepreceding embodiments will only be briefly mentioned because thesecomponents have already been explained in detail above.

Initially, referring to the perspective view of FIG. 24, it can be seenthat the load transducer 800 generally includes a one-piece compacttransducer frame 804 with a central body portion 802 and a plurality ofL-shaped transducer beams 806, 808, 810, 812 connected thereto. As shownin FIG. 24, each of the L-shaped transducer beams 806, 808, 810, 812 isgenerally disposed at a respective corner of the central body portion802.

With reference again to FIG. 24, it can be seen that the illustratedcentral body portion 802 is generally in the form of square band-shapedelement with a central opening 826 disposed therethrough. In FIG. 24, itcan be seen that the body portion 802 comprises a first pair of opposedside portions 802 a, 802 c and a second pair of opposed side portions802 b, 802 d. The side portion 802 a is disposed generally parallel tothe side portion 802 c, while the side portion 802 b is disposedgenerally parallel to the side portion 802 d. Each of the side surfacesof the side portions 802 a, 802 b, 802 c, 802 d is disposed generallyperpendicular to the planar top and bottom surfaces thereof. Also, eachof the first pair of opposed side portions 802 a, 802 c is disposedgenerally perpendicular to each of the second pair of opposed sidesportions 802 b, 802 d. In addition, as shown in FIG. 24, each of thecorners of the central body portion 802 is connected to a respectiveL-shaped transducer beam 806, 808, 810, 812. In the illustratedembodiment, it can be seen that each of the opposed side portions 802 a,802 c comprises a plurality of apertures 828 (e.g., two apertures 828)disposed therethrough for accommodating fasteners (e.g., screws) thatattach the load transducer 800 to another object, such as a robotic arm,etc. Also, as depicted in the FIG. 24, the central body portion 802comprises a raised bottom portion or bottom standoff portion 816 forspacing the L-shaped transducer beams 806, 808, 810, 812 apart from anobject (e.g., robotic arm) to which the load transducer 800 is attachedso that forces and/or moments are capable of being accurately measuredby the load transducer 800.

As shown in FIG. 24, the first generally L-shaped transducer beam 806comprises a first beam portion 806 a and a second beam portion 806 b,wherein the first beam portion 806 a is disposed generally perpendicularto the second beam portion 806 b. Similarly, the second generallyL-shaped transducer beam 808 comprises a first beam portion 808 a and asecond beam portion 808 b, wherein the first beam portion 808 a isdisposed generally perpendicular to the second beam portion 808 b. Also,it can be seen in FIG. 24 that the first beam portion 806 a of the firstgenerally L-shaped transducer beam 806 and the first beam portion 808 aof the second generally L-shaped transducer beam 808 are both generallyaxially aligned with the side portion 802 a of the central body portion802 (i.e., the longitudinal axes of the beam portions 806 a, 808 a aregenerally aligned with the longitudinal axis of the side portion 802 a).With reference again to FIG. 24, the third generally L-shaped transducerbeam 810 comprises a first beam portion 810 a and a second beam portion810 b, wherein the first beam portion 810 a is disposed generallyperpendicular to the second beam portion 810 b. Similarly, the fourthgenerally L-shaped transducer beam 812 comprises a first beam portion812 a and a second beam portion 812 b, wherein the first beam portion812 a is disposed generally perpendicular to the second beam portion 812b. Also, it can be seen in FIG. 24 that the first beam portion 810 a ofthe third generally L-shaped transducer beam 810 and the first beamportion 812 a of the fourth generally L-shaped transducer beam 812 areboth generally axially aligned with the side portion 802 c of thecentral body portion 802 (i.e., the longitudinal axes of the beamportions 810 a, 812 a are generally aligned with the longitudinal axisof the side portion 802 c). Also, in FIG. 24, it can be seen that thefree ends of the second beam portions 806 b, 808 b, 810 b, 812 b of theL-shaped transducer beams 806, 808, 810, 812 are each provided withraised standoff portions 814. Each raised standoff portion 814 isprovided with a mounting aperture 818 disposed therethrough foraccommodating a respective fastener (e.g., a screw) that attaches theload transducer 800 to another object, such as a robotic arm, etc.

As best shown in the perspective view of FIG. 24, the illustrated loadcells are located on the L-shaped transducer beams 806, 808, 810, 812.In the illustrated embodiment, each load cell comprises one or morestrain gages 820, 822, 824. Specifically, in the illustrated embodiment,the second beam portions 806 b, 808 b, 810 b, 812 b of the L-shapedtransducer beams 806, 808, 810, 812 are each provided with a strain gage820 disposed on the top surface thereof that is sensitive to thevertical force component (i.e., an F_(Z) strain gage). In FIG. 24, itcan be seen that each of the strain gages 820 is disposed near theraised standoff portions 818 of the second beam portions 806 b, 808 b,810 b, 812 b. Also, in the illustrated embodiment, the second beamportions 806 b, 808 b, 810 b, 812 b of the L-shaped transducer beams806, 808, 810, 812 each comprise a strain gage 822 disposed on an outerside surface thereof that is sensitive to a first shear force component(i.e., a F_(X) strain gage). The first beam portions 806 a, 808 a, 810a, 812 a of the L-shaped transducer beams 806, 808, 810, 812 eachcomprise a strain gage 824 disposed on an outer side surface thereofthat is sensitive to a second shear force component (i.e., a F_(Y)strain gage).

In the illustrated embodiments of the present invention, the transducerbeams do not extend from a top or upper surface of the central bodyportion. As such, there is no gap formed between the top or uppersurface of the central body portion and a bottom or lower surface of oneor more of the transducer beams. Rather, in the exemplary embodimentscomprising a central body portion, the transducer beams extend outwardlyfrom a side or lateral surface of the central body portion so as tominimize the overall height of the transducer profile (i.e., because thetransducer beams are not required to be disposed above the central bodyportion). Also, in the illustrated embodiments discussed above, thetransducer beams are not in the form of generally linear beams, and arenot in the form of generally linear beams with generally symmetrical endportions. Rather, the transducer beams of the exemplary embodimentsgenerally either emanate from a central body portion and have only onecantilevered end or are arranged in a continuous band-likeconfiguration. In addition, it can be seen that, except for the top andbottom standoff portions on either the transducer beams or the centralbody portions, the top and bottom surfaces of the transducer beams ofthe exemplary embodiments are generally co-planar with the respectivetop and bottom surfaces of the central body portion. Similarly, in theexemplary embodiments having a band-like configuration of transducerbeams, the top surfaces of each of the looped transducer beams aregenerally co-planar with one another, while the bottom surfaces of eachof the looped transducer beams are also generally co-planar with oneanother.

FIGS. 26-29 illustrate a load transducer 900 according to an eleventhexemplary embodiment of the present invention. Referring initially tothe top perspective view of FIG. 26, it can be seen that the loadtransducer 900 generally includes a one-piece compact transducer frame902 having a plurality of transducer beam portions 904, 906, 908, 910,912 connected to one another in succession. As best shown in theperspective views of FIGS. 26 and 29, the plurality of transducer beamportions 904, 906, 908, 910, 912 are arranged in a circumscribingpattern whereby a central one of the plurality of transducer beamportions (i.e., transducer beam portion 904) is at least partiallycircumscribed by one or more outer ones of the plurality of beamportions (i.e., transducer beam portions 906, 908, 910, 912). In otherwords, the plurality of transducer beam portions 904, 906, 908, 910, 912forming the load transducer 900 are arranged in a looped configurationwhereby a central one of the plurality of beam portions (i.e.,transducer beam portion 904) emanates from a generally central locationwithin a footprint of the load transducer 900 and outer ones of theplurality of beam portions (i.e., transducer beam portions 906, 908,910, 912) are wrapped around the central one of the plurality of beamportions. As best illustrated in the perspective views of FIGS. 26 and29, each of the beam portions 908, 910, 912 comprise one or more loadcells or transducer elements for measuring forces and/or moments.

As shown in FIGS. 26-29, the illustrated transducer beam portions 904,906, 908, 910, 912 are arranged in a generally spiral-shaped patternthat emanates from the centrally located transducer beam portion 904.The pattern in which the transducer beam portions 904, 906, 908, 910,912 are arranged is also generally G-shaped (refer to FIGS. 26 and 29).With particular reference to the perspective views of FIGS. 26 and 29,it can be seen that the transducer beam portions 904, 906, 908, 910, 912of the load transducer 900 are arranged in such a configuration thateach of the successive transducer beam portions are disposedsubstantially perpendicular to the immediately preceding transducer beamportion. For example, referring to FIG. 26, the first transducer beamportion 904 is disposed at the approximate center of the transducerfootprint, the second transducer beam portion 906 is connected to thefirst transducer beam portion 904 and is disposed substantiallyperpendicular thereto, the third transducer beam portion 908 isconnected to the second transducer beam portion 906 and is disposedsubstantially perpendicular thereto, the fourth transducer beam portion910 is connected to the third transducer beam portion 908 and isdisposed substantially perpendicular thereto, and the fifth transducerbeam portion 912 is connected to the fourth transducer beam portion 910and is disposed substantially perpendicular thereto. In FIGS. 26 and 29,it can be seen that the transducer beam portions 904, 906, 908, 910, 912of the load transducer 900 are spaced apart from one another by agenerally U-shaped, central gap 942, which is bounded by each of thetransducer beam portions 904, 906, 908, 910, 912. In particular, thefirst transducer beam portion 904 and the third transducer beam portion908, which are disposed generally parallel to one another, are laterallyspaced apart by the gap 942. Similarly, the second transducer beamportion 906 and the fourth transducer beam portion 910, which aredisposed generally parallel to one another, are laterally spaced apartby the gap 942. Also, the first transducer beam portion 904 and thefifth transducer beam portion 912, which are disposed generally parallelto one another, are laterally spaced apart by the gap 942. The thirdtransducer beam portion 908 and the fifth transducer beam portion 912,which are disposed generally parallel to one another, are laterallyspaced apart by the gap 942 and a segment of the first transducer beamportion 904.

Referring again to the top perspective view of FIG. 26, it can be seenthat the first and second transducer beam portions 904, 906 of the loadtransducer 900 together comprise an L-shaped raised portion or standoffportion 920 with mounting apertures 924 (e.g., three apertures 924)disposed therethrough for accommodating fasteners (e.g., screws) thatattach the load transducer 900 to another object, such as a platecomponent of a force plate or force measurement assembly. The mountingapertures 924 pass completely through the first and second transducerbeam portions 904, 906, and are provided with respective bottom boreportions 924 a of increased diameter (see FIG. 29) in order toaccommodate fasteners (e.g., screws) with fillister heads that have alarger outer diameter than the threaded portions of the fasteners. Inaddition, with reference again to FIG. 26, it can be seen that theelevated L-shaped top surface of the first and second transducer beamportions 904, 906 is provided with pin locating bores 926 (e.g., twobores 926) formed therein for receiving locating pins that ensure theproper positioning of the load transducer 900 on the object to which itis mounted, such as a plate component of a force plate or forcemeasurement assembly. The locating pins are received within the pinlocating bores 926 on the load transducer 900 and within correspondingpin locating bores provided on the object (e.g., the force plate orforce measurement assembly). As depicted in the bottom perspective viewof FIG. 29, the fifth transducer beam portion 912 of the load transducer900 comprises a generally rectangular or square raised portion orstandoff portion 922 with a mounting aperture 928 (e.g., a singleaperture 928) disposed therethrough for accommodating a fastener (e.g.,a screw) that attaches the load transducer 900 to another object, suchas a mounting foot of a force plate or force measurement assembly.Advantageously, the standoff portions 920, 922 on the top and bottom ofthe load transducer 900 elevate the transducer beam portions 904, 906,908, 910, 912 above the object(s) to which the load transducer 900 isattached so that forces and/or moments are capable of being accuratelymeasured by the load transducer 900. In one or more embodiments, thestructural components to which the load transducer 900 is mounted areconnected only to the top standoff portion 920 and the bottom standoff922 so as to ensure that the total load applied to the load transducer900 is transmitted through the transducer beam portions 904, 906, 908,910, 912.

In the illustrative embodiment, the third, fourth, and fifth transducerbeam portions 908, 910, 912 have a top surface that is disposed at afirst elevation relative to a bottom surface of the load transducer 900,whereas the L-shaped raised portion 920 of the first and secondtransducer beam portions 904, 906 has a top surface that is disposed ata second elevation relative to the bottom surface of the load transducer900. As best shown in FIGS. 26-28, the second elevation is greater thanthe first elevation such that a recessed area is created by thedifference in elevation between the second elevation and the firstelevation. In the illustrated embodiment, the recessed area is used toaccommodate electrical components of the transducer load cells (e.g.,strain gages 934, 936 a, 938 a).

In the illustrative embodiment of FIGS. 26-29, each of the transducerbeam portions 908, 910, 912 is provided with a respective aperture 914,916, 918 disposed therethrough. In particular, the third transducer beamportion 908 is provided with a generally rectangular aperture 914disposed vertically through the beam portion. Similarly, the fourthtransducer beam portion 910 is provided with a generally rectangularaperture 916 disposed vertically through the beam portion. The fifthtransducer beam portion 912 is provided with a generally rectangularaperture 918 disposed horizontally through the beam portion. Theapertures 914, 916, 918, which are disposed through the respectivetransducer beam portions 908, 910, 912, significantly increase thesensitivity of the load transducer 900 when a load is applied thereto byreducing the cross-sectional area of the transducer beam portions 908,910, 912 at the locations of the apertures 914, 916, 918.

As best shown in the perspective views of FIGS. 26 and 29, theillustrated load cells are located on the transducer beam portions 908,910, 912. In the illustrated embodiment, each load cell comprises one ormore strain gages 930, 932, 934, 936 a, 936 b, 938 a, 938 b, 940 a, and940 b. Specifically, in the illustrated embodiment, the third transducerbeam portion 908 of the load transducer 900 comprises a strain gage 932disposed on a side surface thereof that is sensitive to a first shearforce component (i.e., a F_(Y) strain gage) and substantially centeredon the aperture 914. The third transducer beam portion 908 alsocomprises a set of strain gages 938 a, 938 b that are sensitive to afirst moment component (i.e., a M_(Y) strain gages). The strain gages938 a, 938 b are disposed on opposed side surfaces (e.g., top and bottomsurfaces) of the third transducer beam portion 908, and aresubstantially vertically aligned with one another. Turning again toFIGS. 26 and 29, in the illustrated embodiment, the fourth transducerbeam portion 910 of the load transducer 900 comprises a strain gage 930disposed on a side surface thereof that is sensitive to a second shearforce component (i.e., a F_(X) strain gage) and substantially centeredon the aperture 916. The fourth transducer beam portion 910 alsocomprises a set of strain gages 936 a, 936 b that are sensitive to asecond moment component (i.e., a M_(X) strain gages). Like the straingages 938 a, 938 b, the strain gages 936 a, 936 b are disposed onopposed side surfaces (e.g., top and bottom surfaces) of the fourthtransducer beam portion 910, and are substantially vertically alignedwith one another. With reference again to FIGS. 26 and 29, in theillustrated embodiment, the fifth transducer beam portion 912 of theload transducer 900 comprises a strain gage 934 disposed on the topsurface thereof that is sensitive to a vertical force component (i.e., aF_(Z) strain gage) and substantially centered on the aperture 918. Thefifth transducer beam portion 912 also comprises a set of strain gages940 a, 940 b that are sensitive to a third moment component (i.e., aM_(Z) strain gages). Like the strain gages 936 a, 936 b and 938 a, 938b, the strain gages 940 a, 940 b are disposed on opposed side surfaces(e.g., first and second lateral surfaces) of the fifth transducer beamportion 912, and are substantially horizontally aligned with oneanother. In the illustrated embodiment, the first shear force componentis generally perpendicular to the second shear force component, and eachof the first and second shear force components are generallyperpendicular to the vertical force component.

In the illustrated embodiment, the strain gages 930, 932, 934 aredisposed on respective outer surfaces of the transducer beam portions910, 908, 912. The outer surfaces of the transducer beam portions 910,908, 912 on which the strain gages 930, 932, 934 are disposed aregenerally opposite to the inner surfaces of the respective apertures916, 914, 918.

As best shown in FIGS. 26 and 29, the illustrated load cells are mountedon top, bottom, or side surfaces of the transducer beam portions 908,910, 912 between the standoff portions 920, 922 of the load transducer900. Alternatively, the strain gages 932, 930 can be mounted to theinner side surfaces of the respective third and fourth transducer beamportions 908, 910, rather than to the outer side surfaces of therespective third and fourth transducer beam portions 908, 910 asillustrated in FIGS. 26 and 29. Similarly, the strain gage 934 can bemounted to the bottom surface of the fifth transducer beam portion 912,rather than to the top of the transducer beam portion 912 as illustratedin FIG. 26. In general, the strain gages 930, 932, 934 are mounted tosurfaces generally normal to the direction of applied vertical and/orshear forces (i.e., F_(X), F_(Y), F_(Z)). It is also noted thatalternatively, strain gages 930 can be mounted at both opposed sidesurfaces of fourth transducer beam portion 910 and/or strain gages 932can be mounted at both opposed side surfaces of the third transducerbeam portion 908. Similarly, strain gages 934 can be mounted at both thetop surface and the bottom surface of the fifth transducer beam portion912. These strain gages 930, 932, 934 measure force either by bendingmoment or difference of bending moments at two cross sections. As forceis applied to the ends of the load transducer 900, the transducer beamportions bend. This bending either stretches or compresses the straingages 930, 932, 934, which in turn changes the resistance of theelectrical current passing therethrough. The amount of change in theelectrical voltage or current is proportional to the magnitude of theapplied force, as applied to the L-shaped standoff portion 920.

In the illustrated embodiment, each of the strain gages 930, 932, 934comprises a full-bridge strain gage configuration (i.e., four (4) activestrain gage elements wired in a Wheatstone bridge configuration), whileeach of the strain gages 936 a, 936 b, 938 a, 938 b, 940 a, and 940 bcomprises a half-bridge strain gage configuration (i.e., two (2) activestrain gage elements). Also, in the illustrative embodiment, the pair ofstrain gages 936 a, 936 b are wired together in one Wheatstone bridgeconfiguration (i.e., with a total of four (4) active strain gageelements), the pair of strain gages 938 a, 938 b are wired together inanother Wheatstone bridge configuration (i.e., with a total of four (4)active strain gage elements), and the pair of strain gages 940 a, 940 bare wired together in yet another Wheatstone bridge configuration (i.e.,with a total of four (4) active strain gage elements).

FIGS. 30-33 illustrate a load transducer 1000 according to a twelfthexemplary embodiment of the present invention. With reference to thesefigures, it can be seen that the load transducer 1000 is similar in manyrespects to the load transducer 900 of the eleventh embodiment describedabove. However, unlike the aforedescribed load transducer 900, the loadtransducer 1000 only measures the force components of a load (i.e.,F_(X), F_(Y), F_(Z)), rather than both the force and moment componentsof a load as explained above with regard to the load transducer 1000.

Initially, referring to the top perspective view of FIG. 30, it can beseen that the load transducer 1000 generally includes a one-piececompact transducer frame 1002 having a plurality of transducer beamportions 1004, 1006, 1008, 1010, 1012 connected to one another insuccession. As best shown in the perspective views of FIGS. 30 and 33,the plurality of transducer beam portions 1004, 1006, 1008, 1010, 1012are arranged in a circumscribing pattern whereby a central one of theplurality of transducer beam portions (i.e., transducer beam portion1004) is at least partially circumscribed by one or more outer ones ofthe plurality of beam portions (i.e., transducer beam portions 1006,1008, 1010, 1012). In other words, the plurality of transducer beamportions 1004, 1006, 1008, 1010, 1012 forming the load transducer 1000are arranged in a looped configuration whereby a central one of theplurality of beam portions (i.e., transducer beam portion 1004) emanatesfrom a generally central location within a footprint of the loadtransducer 1000 and outer ones of the plurality of beam portions (i.e.,transducer beam portions 1006, 1008, 1010, 1012) are wrapped around thecentral one of the plurality of beam portions. As best illustrated inthe perspective views of FIGS. 30 and 33, each of the beam portions1008, 1010, 1012 comprise one or more load cells or transducer elementsfor measuring the various components of an applied force.

As shown in FIGS. 30-33, the illustrated transducer beam portions 1004,1006, 1008, 1010, 1012 are arranged in a generally spiral-shaped patternthat emanates from the centrally located transducer beam portion 1004.The pattern in which the transducer beam portions 1004, 1006, 1008,1010, 1012 are arranged is also generally G-shaped (refer to FIGS. 30and 33). With particular reference to the perspective views of FIGS. 30and 33, it can be seen that the transducer beam portions 1004, 1006,1008, 1010, 1012 of the load transducer 1000 are arranged in such aconfiguration that each of the successive transducer beam portions aredisposed substantially perpendicular to the immediately precedingtransducer beam portion. For example, referring to FIG. 30, the firsttransducer beam portion 1004 is disposed at the approximate center ofthe transducer footprint, the second transducer beam portion 1006 isconnected to the first transducer beam portion 1004 and is disposedsubstantially perpendicular thereto, the third transducer beam portion1008 is connected to the second transducer beam portion 1006 and isdisposed substantially perpendicular thereto, the fourth transducer beamportion 1010 is connected to the third transducer beam portion 1008 andis disposed substantially perpendicular thereto, and the fifthtransducer beam portion 1012 is connected to the fourth transducer beamportion 1010 and is disposed substantially perpendicular thereto. InFIGS. 30 and 33, it can be seen that the transducer beam portions 1004,1006, 1008, 1010, 1012 of the load transducer 1000 are spaced apart fromone another by a generally U-shaped, central gap 1032, which is boundedby each of the transducer beam portions 1004, 1006, 1008, 1010, 1012. Inparticular, the first transducer beam portion 1004 and the thirdtransducer beam portion 1008, which are disposed generally parallel toone another, are laterally spaced apart by the gap 1032. Similarly, thesecond transducer beam portion 1006 and the fourth transducer beamportion 1010, which are disposed generally parallel to one another, arelaterally spaced apart by the gap 1032. Also, the first transducer beamportion 1004 and the fifth transducer beam portion 1012, which aredisposed generally parallel to one another, are laterally spaced apartby the gap 1032. The third transducer beam portion 1008 and the fifthtransducer beam portion 1012, which are disposed generally parallel toone another, are laterally spaced apart by the gap 1032 and a segment ofthe first transducer beam portion 1004.

Referring again to the top perspective view of FIG. 30, it can be seenthat the first and second transducer beam portions 1004, 1006 of theload transducer 1000 comprise an L-shaped arrangement of mountingapertures 1020 (e.g., three (3) apertures 1020) disposed therethroughfor accommodating fasteners (e.g., screws) that attach the loadtransducer 1000 to another object, such as a plate component of a forceplate or force measurement assembly. The mounting apertures 1020 passcompletely through the first and second transducer beam portions 1004,1006, and are provided with respective bottom bore portions 1020 a ofincreased diameter (see FIG. 33) in order to accommodate fasteners(e.g., screws) with fillister heads that have a larger outer diameterthan the threaded portions of the fasteners. In addition, with referenceagain to FIG. 30, it can be seen that the L-shaped portion of the loadtransducer 1000 that is formed by the first and second transducer beamportions 1004, 1006 is provided with pin locating bores 1022 (e.g., two(2) bores 1022) formed therein for receiving locating pins that ensurethe proper positioning of the load transducer 1000 on the object towhich it is mounted, such as a plate component of a force plate or forcemeasurement assembly. The locating pins are received within the pinlocating bores 1022 on the load transducer 1000 and within correspondingpin locating apertures provided on the object (e.g., the force plate orforce measurement assembly). As depicted in the perspective views ofFIGS. 30 and 33, the fifth transducer beam portion 1012 of the loadtransducer 1000 comprises a mounting aperture 1024 (e.g., a singleaperture 1024 proximate to the free end thereof) disposed therethroughfor accommodating a fastener (e.g., a screw) that attaches the loadtransducer 1000 to another object, such as a mounting foot of a forceplate or force measurement assembly. In one or more embodiments, theload transducer 1000 is connected to one or more objects in such amanner that the total load applied to the load transducer 1000 istransmitted through the transducer beam portions 1004, 1006, 1008, 1010,1012.

In the illustrative embodiment of FIGS. 30-33, each of the transducerbeam portions 1008, 1010, 1012 is provided with a respective aperture1014, 1016, 1018 disposed therethrough. In particular, the thirdtransducer beam portion 1008 is provided with a generally rectangularaperture 1014 disposed vertically through the beam portion. Similarly,the fourth transducer beam portion 1010 is provided with a generallyrectangular aperture 1016 disposed vertically through the beam portion.The fifth transducer beam portion 1012 is provided with a generallyrectangular aperture 1018 disposed horizontally through the beamportion. The apertures 1014, 1016, 1018, which are disposed through therespective transducer beam portions 1008, 1010, 1012, significantlyincrease the sensitivity of the load transducer 1000 when a load isapplied thereto by reducing the cross-sectional area of the transducerbeam portions 1008, 1010, 1012 at the locations of the apertures 1014,1016, 1018.

As best shown in the perspective views of FIGS. 30 and 33, theillustrated load cells are located on the transducer beam portions 1008,1010, 1012. In the illustrated embodiment, each load cell comprises oneor more strain gages 1026, 1028, and 1030. Specifically, in theillustrated embodiment, the third transducer beam portion 1008 of theload transducer 1000 comprises a strain gage 1028 disposed on a sidesurface thereof that is sensitive to a first shear force component(i.e., a F_(Y) strain gage) and substantially centered on the aperture1014. Turning again to FIGS. 30 and 33, in the illustrated embodiment,the fourth transducer beam portion 1010 of the load transducer 1000comprises a strain gage 1026 disposed on a side surface thereof that issensitive to a second shear force component (i.e., a F_(X) strain gage)and substantially centered on the aperture 1016. With reference again toFIGS. 30 and 33, in the illustrated embodiment, the fifth transducerbeam portion 1012 of the load transducer 1000 comprises a strain gage1030 disposed on the top surface thereof that is sensitive to a verticalforce component (i.e., a F_(Z) strain gage) and substantially centeredon the aperture 1018. In the illustrated embodiment, the first shearforce component is generally perpendicular to the second shear forcecomponent, and each of the first and second shear force components aregenerally perpendicular to the vertical force component.

In the illustrated embodiment, the strain gages 1026, 1028, 1030 aredisposed on respective outer surfaces of the transducer beam portions1010, 1008, 1012. The outer surfaces of the transducer beam portions1010, 1008, 1012 on which the strain gages 1026, 1028, 1030 are disposedare generally opposite to the inner surfaces of the respective apertures1016, 1014, 1018.

As best shown in FIGS. 30 and 33, the illustrated load cells are mountedon top or side surfaces of the transducer beam portions 1008, 1010, 1012between the ends of the load transducer 1000. Alternatively, the straingages 1028, 1026 can be mounted to the inner side surfaces of therespective third and fourth transducer beam portions 1008, 1010, ratherthan to the outer side surfaces of the respective third and fourthtransducer beam portions 1008, 1010 as illustrated in FIGS. 30 and 33.Similarly, the strain gage 1030 can be mounted to the bottom surface ofthe fifth transducer beam portion 1012, rather than to the top of thetransducer beam portion 1012 as illustrated in FIG. 30. In general, thestrain gages 1026, 1028, 1030 are mounted to surfaces generally normalto the direction of applied vertical and/or shear forces (i.e., F_(X),F_(Y), F_(Z)). It is also noted that alternatively, strain gages 1026can be mounted at both opposed side surfaces of fourth transducer beamportion 1010 and/or strain gages 1028 can be mounted at both opposedside surfaces of the third transducer beam portion 1008. Similarly,strain gages 1030 can be mounted at both the top surface and the bottomsurface of the fifth transducer beam portion 1012. These strain gages1026, 1028, 1030 measure force either by bending moment or difference ofbending moments at two cross sections. As force is applied to the endsof the load transducer 1000, the transducer beam portions bend. Thisbending either stretches or compresses the strain gages 1026, 1028,1030, which in turn changes the resistance of the electrical currentpassing therethrough. The amount of change in the electrical voltage orcurrent is proportional to the magnitude of the applied force, asapplied to the load transducer 1000.

In the illustrated embodiment, each of the strain gages 1026, 1028, 1030comprises a full-bridge strain gage configuration (i.e., four (4) activestrain gage elements wired in a Wheatstone bridge configuration) formeasuring the applied vertical and shear forces.

An exemplary embodiment of a force measurement system is illustrated inFIGS. 34-37. In the illustrative embodiment, the force measurementsystem generally comprises a force measurement assembly 1040 (i.e., aforce plate) that is operatively coupled to a data acquisition/dataprocessing device 1060 (i.e., a data acquisition and processing deviceor computing device that is capable of collecting, storing, andprocessing data). The force measurement assembly 1040 illustrated inFIGS. 34-36 is configured to receive a subject thereon, and is capableof measuring the forces and/or moments applied to its measurementsurface by the subject.

As shown in FIG. 34, the data acquisition and processing device 1060(e.g., in the form of a laptop digital computer) generally includes abase portion 1064 with a central processing unit (CPU) disposed thereinfor collecting and processing the data that is received from the forcemeasurement assembly 1040, and a plurality of devices 1066-1070operatively coupled to the central processing unit (CPU) in the baseportion 1064. Preferably, the devices that are operatively coupled tothe central processing unit (CPU) comprise user input devices 1066, 1068in the form of a keyboard 1066 and a touchpad 1068, as well as agraphical user interface in the form of a laptop LCD screen 1070. Whilea laptop type computing system is depicted in the embodiment of FIG. 34,one of ordinary skill in the art will appreciate that another type ofdata acquisition and processing device 1060 can be substituted for thelaptop computing system such as, but not limited to, a palmtop computingdevice (i.e., a PDA) or a desktop type computing system having aplurality of separate, operatively coupled components (e.g., a desktoptype computing system including a main housing with a central processingunit (CPU) and data storage devices, a remote monitor, a remotekeyboard, and a remote mouse).

As illustrated in FIG. 34, force measurement assembly 1040 isoperatively coupled to the data acquisition/data processing device 1060by virtue of an electrical cable 1062. In one embodiment of theinvention, the electrical cable 1062 is used for data transmission, aswell as for providing power to the force measurement assembly 1040.Various types of data transmission cables can be used for cable 1062.For example, the cable 1062 can be a Universal Serial Bus (USB) cable oran Ethernet cable. Preferably, the electrical cable 1062 contains aplurality of electrical wires bundled together, with at least one wirebeing used for power and at least another wire being used fortransmitting data. The bundling of the power and data transmission wiresinto a single electrical cable 1062 advantageously creates a simpler andmore efficient design. In addition, it enhances the safety of thetesting environment when human subjects are being tested on the forcemeasurement assembly 1040. However, it is to be understood that theforce measurement assembly 1040 can be operatively coupled to the dataacquisition/data processing device 1040 using other signal transmissionmeans, such as a wireless data transmission system. If a wireless datatransmission system is employed, it is preferable to provide the forcemeasurement assembly 1040 with a separate power supply in the form of aninternal power supply or a dedicated external power supply.

Referring again to FIG. 34, it can be seen that the force measurementassembly 1040 of the illustrated embodiment is in the form of a forceplate assembly with a single, continuous measurement surface. The forceplate assembly includes a plate component 1042 supported on a pluralityof load transducers 1000, 1000′. As shown in FIGS. 34 and 35, the platecomponent 1042 comprises a top measurement surface 1044, a bottomsurface 1054 disposed generally opposite to the top measurement surface1044, and a plurality of side surfaces 1046, 1048, 1050, 1052 disposedbetween the top and bottom surfaces 1044, 1054. In the illustratedembodiment, the first side surface 1046 of the plate component 1042 isdisposed generally parallel to the second side surface 1048, and isdisposed generally perpendicular to both the third side surface 1050 andthe fourth side surface 1052. The third side surface 1050 of the platecomponent 1042 is disposed generally parallel to the fourth side surface1052, and is disposed generally perpendicular to both the first sidesurface 1046 and the second side surface 1048. Turning to the explodedview of FIG. 36, it can be seen that the bottom surface 1054 of theplate component 1042 comprises a plurality of transducer mountingrecesses 1056 for accommodating respective ones of the load transducers1000, 1000′. Also, as shown in FIG. 36, it can be seen that an L-shapedtransducer standoff plate 1034 is provided in each of the transducermounting recesses 1056 for spacing the top surfaces of the loadtransducers 1000, 1000′ from the mounting surfaces of the recesses 1056.Referring again to the bottom perspective view of FIG. 36, it can beseen that each L-shaped transducer standoff plate 1034 comprises aplurality of mounting apertures 1036 (e.g., three (3) apertures 1036)disposed therethrough for accommodating fasteners (e.g., screws) thatattach the plate component 1042 of the force measurement assembly 1040to either the load transducer 1000 or the load transducer 1000′. Assuch, the mounting apertures 1036 in each L-shaped transducer standoffplate 1034 are substantially aligned with the mounting apertures 1020 inthe load transducers 1000, 1000′ such that they correspond thereto. Inaddition, with reference again to FIG. 36, it can be seen that eachL-shaped transducer standoff plate 1034 further comprises pin locatingapertures 1038 (e.g., two (2) apertures 1038) formed therein forreceiving locating pins that ensure the proper positioning of the loadtransducers 1000, 1000′ on the plate component 1042 of the forcemeasurement assembly 1040. Thus, the pin locating apertures 1038 in eachL-shaped transducer standoff plate 1034 are substantially aligned withthe pin locating bores 1022 in the load transducers 1000, 1000′ suchthat they correspond thereto. The pin locating apertures 1038 in theL-shaped transducer standoff plates 1034, and the pin locating bores1022 in the load transducers 1000, 1000′, collectively receive locatingpins that ensure the proper positioning of the load transducers 1000,1000′ on the plate component 1042 of the force measurement assembly1040.

In illustrated embodiment of FIGS. 34-36, the force measurement assembly1040 comprises a total of four (4) load transducers 1000, 1000′ that aredisposed underneath, and near each of the respective four corners (4) ofthe plate component 1042. The load transducers 1000′ are generally thesame as the load transducers 1000, expect that they are configured as amirror image of the load transducers 1000. Advantageously, because theload transducers 1000, 1000′ are compact, none of the plurality of loadtransducers 1000, 1000′ extend substantially an entire length or widthof the plate component 1042 of the force measurement assembly 1040. Thecompact construction of the load transducers 1000, 1000′ not onlyreduces material costs because less material is used to form the loadtransducers 1000, 1000′, but it also allows the load transducers 1000,1000′ to be universally used on force plates having a myriad ofdifferent lengths and widths because it is not necessary for the loadtransducers 1000, 1000′ to conform to the footprint size of the forceplate.

In an alternative embodiment, rather than using the load transducers1000, 1000′ on the force measurement assembly 1040, the load transducers900 described above could be provided on the force measurement assembly1040. Using the load transducers 900 in lieu of the load transducers1000, 1000′ would enable the moment components of the load applied tothe plate component 1042 to be measured in addition to the forcecomponents of the load.

In other embodiments of the invention, rather than using a forcemeasurement assembly 1040 having a plate component 1042 with a singlemeasurement surface 1044, it is to be understood that a forcemeasurement assembly in the form of a dual force plate may bealternatively employed. Unlike the single force plate assembly 1040illustrated in FIGS. 34-36, the dual force plate comprises two separateplate components, each of which is configured to accommodate arespective one of a subject's feet thereon (i.e., the left platecomponent accommodates the subject's left foot, whereas the right platecomponent accommodates the subject's right foot). In these alternativeembodiments, each of the two plate components of the dual force plateare supported on four (4) load transducers 1000, 1000′ (i.e., a loadtransducer 1000, 1000′ is disposed in each of the respective four (4)corners of each of the two plate components). As such, the dual forceplate comprises a total of eight (8) load transducers 1000, 1000′ (i.e.,four (4) load transducers 1000, 1000′ under each of the two platecomponents).

Also, as shown in FIGS. 34-36, the force measurement assembly 1040 isprovided with a plurality of support feet 1058 disposed thereunder.Preferably, each of the four (4) corners of the force measurementassembly 1040 is provided with a support foot 1058 (e.g., mounted on thebottom of each load transducer 1000, 1000′). In particular, in theillustrated embodiment, each support foot 1058 is attached to anaperture 1024 in a respective one of the load transducers 1000, 1000′ bymeans of a fastener (e.g., a screw). In one embodiment, at least one ofthe support feet 1058 is adjustable so as to facilitate the leveling ofthe force measurement assembly 1040 on an uneven floor surface.

Now, turning to FIG. 37, it can be seen that the data acquisition/dataprocessing device 1060 (i.e., the laptop computing device) of the forcemeasurement system comprises a microprocessor 1060 a for processingdata, memory 1060 b (e.g., random access memory or RAM) for storing dataduring the processing thereof, and data storage device(s) 1060 c, suchas one or more hard drives, compact disk drives, floppy disk drives,flash drives, or any combination thereof. As shown in FIG. 37, the forcemeasurement assembly 1040 and the visual display device 1070 areoperatively coupled to the core components 1060 a, 1060 b, 1060 c of thedata acquisition/data processing device 1060 such that data is capableof being transferred between these devices 1040, 1060 a, 1060 b, 1060 c,and 1070. Also, as illustrated in FIG. 37, a plurality of data inputdevices 1066, 1068 such as the keyboard 1066 and mouse 1068 shown inFIG. 34, are operatively coupled to the core components 1060 a, 1060 b,1060 c of the data acquisition/data processing device 1060 so that auser is able to enter data into the data acquisition/data processingdevice 1060. In some embodiments, the data acquisition/data processingdevice 1060 can be in the form of a laptop computer, while in otherembodiments, the data acquisition/data processing device 1060 can beembodied as a desktop computer.

FIG. 38 graphically illustrates the acquisition and processing of theload data carried out by the exemplary force measurement system of FIG.34. Initially, as shown in FIG. 38, a load L is applied to the forcemeasurement assembly 1040 (e.g., by a subject disposed thereon). Theload is transmitted from the plate component 1042 to the loadtransducers 1000, 1000′ disposed in each of its four (4) corners. Asdescribed above, in the illustrated embodiment, each of the loadtransducers 1000, 1000′ includes a plurality of strain gages 1026, 1028,1030 wired in one or more Wheatstone bridge configurations, wherein theelectrical resistance of each strain gage is altered when the associatedbeam portion of the load transducer 1000, 1000′ undergoes deformationresulting from the load (i.e., forces and/or moments) acting on theplate component 1042. For each plurality of strain gages disposed on theload transducers 1000, 1000′, the change in the electrical resistance ofthe strain gages brings about a consequential change in the outputvoltage of the Wheatstone bridge (i.e., a quantity representative of theload being applied to the measurement surface 1044). Thus, in oneembodiment, the four (4) load transducers 1000, 1000′ disposed under theplate component 1042 output a total of twelve (12) analog outputvoltages (signals). In some embodiments, the twelve (12) analog outputvoltages from load transducers 1000, 1000′ disposed under the platecomponent 1042 are then transmitted to a preamplifier board (not shown)for preconditioning. The preamplifier board is used to increase themagnitudes of the transducer analog voltages, and preferably, to convertthe analog voltage signals into digital voltage signals as well. Afterwhich, the force measurement assembly 1040 transmits the force plateoutput signals S_(FPO1)-S_(FP12) to a main signal amplifier/converter1072. Depending on whether the preamplifier board also includes ananalog-to-digital (A/D) converter, the force plate output signalsS_(FPO1)-S_(FP12) could be either in the form of analog signals ordigital signals. The main signal amplifier/converter 1072 furthermagnifies the force plate output signals S_(FPO1)-S_(FP12), and if thesignals S_(FPO1)-S_(FP12) are of the analog-type (for a case where thepreamplifier board did not include an analog-to-digital (A/D)converter), it may also convert the analog signals to digital signals.Then, the signal amplifier/converter 1072 transmits either the digitalor analog signals S_(ACO1)-S_(AC12) to the data acquisition/dataprocessing device 1060 (computer 1060) so that the forces and/or momentsthat are being applied to the measurement surface 1044 of the forcemeasurement assembly 1040 can be transformed into output load values OL.In addition to the components 1060 a, 1060 b, 1060 c, the dataacquisition/data processing device 1060 may further comprise ananalog-to-digital (A/D) converter if the signals S_(ACO1)-S_(AC12) arein the form of analog signals. In such a case, the analog-to-digitalconverter will convert the analog signals into digital signals forprocessing by the microprocessor 1060 a.

When the data acquisition/data processing device 1060 receives thevoltage signals S_(ACO1)-S_(AC12), it initially transforms the signalsinto output forces by multiplying the voltage signals S_(ACO1)-S_(AC12)by a calibration matrix. If the load transducer 900 is used inconjunction with the force measurement assembly 1040, the dataacquisition/data processing device 1060 may additionally transform thesignals into output moments by multiplying the voltage signals by thecalibration matrix. After which, the force exerted on the surface 1044of the force measurement assembly 1040, and the center of pressure ofthe applied force (i.e., the x and y coordinates of the point ofapplication of the force applied to the measurement surface 1044) isdetermined by the data acquisition/data processing device 1060.Referring to the perspective view of FIG. 34, it can be seen that thecenter of pressure coordinates (x_(P) _(L) , y_(P) _(L) ) for the platecomponent 1042 of the force measurement assembly 1040 are determined inaccordance with x and y coordinate axes 1074, 1076.

In one exemplary embodiment, the data acquisition/data processing device1060 determines all three (3) orthogonal components of the resultantforces acting on the plate component 1042 of the force measurementassembly 1040 (i.e., F_(X), F_(Y), F_(Z)). In yet other embodiments ofthe invention, all three (3) orthogonal components of the resultantforces and moments acting on the plate component 1042 of the forcemeasurement assembly 1040 (i.e., F_(X), F_(Y), F_(Z), M_(X), M_(Y),M_(Z)) may be determined (i.e., when the load transducer 900 is used inlieu of the load transducers 1000, 1000′).

FIGS. 39-41 illustrate a load transducer 1100 according to a thirteenthexemplary embodiment of the present invention. Referring initially tothe perspective view of FIG. 39, it can be seen that the load transducer1100 generally includes a one-piece compact transducer frame 1104 havinga central body portion 1102 and a plurality of beam portions 1106, 1108,1110, 1112 extending along sides 1102 a, 1102 b, 1102 c of the centralbody portion 1102. As best illustrated in the perspective view of FIG.39, each of the beam portions 1106, 1108, 1110, 1112 comprises one ormore load cells or transducer elements for measuring forces and/ormoments.

With reference again to FIG. 39, it can be seen that the illustratedcentral body portion 1102 is generally in the form of a square prismwith substantially right angle corners (i.e., substantially 90 degreecorners). In FIG. 39, it can be seen that the body portion 1102comprises a first pair of opposed sides 1102 a, 1102 c and a second pairof opposed sides 1102 b, 1102 d. The side 1102 a is disposed generallyparallel to the side 1102 c, while the side 1102 b is disposed generallyparallel to the side 1102 d. Each of the sides 1102 a, 1102 b, 1102 c,1102 d is disposed generally perpendicular to the planar top and bottomsurfaces of the body portion 1102. Also, each of the first pair ofopposed sides 1102 a, 1102 c is disposed generally perpendicular to eachof the second pair of opposed sides 1102 b, 1102 d. In addition, asshown in FIG. 39, the second side 1102 b comprises a beam connectingportion 1114 extending outward therefrom. In the illustrated embodiment,it can be seen that the beam connecting portion 1114 connects the beamportions 1106 and 1110 to the second side 1102 b of the central bodyportion 1102. In the illustrated embodiment, the total load applied tothe load transducer 1100 is transmitted through the beam portions 1106,1108, 1110, 1112.

As best shown in FIGS. 39 and 41, the proximal end of the first beamportion 1106 is rigidly connected to the central body portion 1102 bymeans of the beam connecting portion 1114, and the distal end of thefirst beam portion 1106 is rigidly connected to the proximal end of thesecond beam portion 1108. As depicted in these figures, the first beamportion 1106 extends along the second side 1102 b of the central bodyportion 1102, and the second beam portion 1108 extends along the firstside 1102 a of the central body portion 1102. More particularly, in theillustrative embodiment, the longitudinal axis of the first beam portion1106 is disposed generally parallel to the second side 1102 b of thecentral body portion 1102, and the longitudinal axis of the second beamportion 1108 is disposed generally parallel to the first side 1102 a ofthe central body portion 1102. As best shown in the perspective view ofFIG. 39, the top and bottom surfaces of each of the first and secondbeam portions 1106, 1108 are disposed substantially co-planar with thetop and bottom surfaces of the central body portion 1102. Also, in theillustrative embodiment, with reference again to FIGS. 39 and 41, thefirst beam portion 1106 is generally perpendicular, or perpendicular tothe second beam portion 1108 (i.e., together the first and second beamportions 1106, 1108 form an overall L-shaped beam arm). In addition, asshown in these figures, the first beam portion 1106 is spaced apart fromthe second side 1102 b of the central body portion 1102 by a first gap1128, and the second beam portion 1108 is spaced apart from the firstside 1102 a of the central body portion 1102 by a second gap 1130. Inthe illustrative embodiment, together the first gap 1128 and the secondgap 1130 form an overall L-shaped gap (i.e., the first gap 1128 isdisposed perpendicular to the second gap 1130).

Also, referring again to FIGS. 39 and 41, it can be seen that theproximal end of the third beam portion 1110 is rigidly connected to thecentral body portion 1102 by means of the beam connecting portion 1114,and the distal end of the third beam portion 1110 is rigidly connectedto the proximal end of the fourth beam portion 1112. As depicted inthese figures, the third beam portion 1110 extends along the second side1102 b of the central body portion 1102, and the fourth beam portion1112 extends along the third side 1102 c of the central body portion1102. More particularly, in the illustrative embodiment, thelongitudinal axis of the third beam portion 1110 is disposed generallyparallel to the second side 1102 b of the central body portion 1102, andthe longitudinal axis of the fourth beam portion 1112 is disposedgenerally parallel to the third side 1102 c of the central body portion1102. As best shown in the perspective view of FIG. 39, the top andbottom surfaces of each of the third and fourth beam portions 1110, 1112are disposed substantially co-planar with the top and bottom surfaces ofthe central body portion 1102. Also, in the illustrative embodiment,with reference again to FIGS. 39 and 41, the third beam portion 1110 isgenerally perpendicular, or perpendicular to the fourth beam portion1112 (i.e., together the third and fourth beam portions 1110, 1112 forman overall L-shaped beam arm). In addition, as shown in these figures,the third beam portion 1110 is spaced apart from the second side 1102 bof the central body portion 1102 by a third gap 1132, and the fourthbeam portion 1112 is spaced apart from the third side 1102 c of thecentral body portion 1102 by a fourth gap 1134. In the illustrativeembodiment, together the third gap 1132 and the fourth gap 1134 form anoverall L-shaped gap (i.e., the third gap 1132 is disposed perpendicularto the fourth gap 1134).

In the illustrative embodiment of FIGS. 39 and 41, it can be seen thatthe free end 1108 a of the second beam portion 1108 is generallyaligned, or aligned with the fourth side 1102 d of the central bodyportion 1102 (i.e., the end face of the second beam portion 1108 isco-planar with the fourth side 1102 d of the central body portion 1102).Also, as shown in FIGS. 39 and 41, the free end 1112 a of the fourthbeam portion 1112 is generally aligned, or aligned with the fourth side1102 d of the central body portion 1102 (i.e., the end face of thefourth beam portion 1112 is co-planar with the fourth side 1102 d of thecentral body portion 1102).

In the illustrative embodiment of FIGS. 39-41, the first beam portion1106 is provided with an aperture 1116 disposed therethrough, the secondbeam portion 1108 is provided with apertures 1118, 1120 disposedtherethrough, the third beam portion 1110 is provided with an aperture1122 disposed therethrough, and the fourth beam portion 1112 is providedwith apertures 1124, 1126 disposed therethrough. In particular, thefirst and third transducer beam portions 1106, 1110 are provided withrespective generally rectangular apertures 1116, 1122 disposedvertically through the beam portions 1106, 1110. The second transducerbeam portion 1108 is provided with a first generally rectangularaperture 1118 disposed vertically through the beam portion 1108 and asecond generally rectangular aperture 1120 disposed horizontally throughthe beam portion 1108. As such, the vertically extending aperture 1118of the second beam portion 1108 extends in a direction that is generallyperpendicular, or perpendicular to the extending direction of thehorizontally extending aperture 1120. Similarly, the fourth transducerbeam portion 1112 is provided with a first generally rectangularaperture 1124 disposed vertically through the beam portion 1112 and asecond generally rectangular aperture 1126 disposed horizontally throughthe beam portion 1112. As such, the vertically extending aperture 1124of the fourth beam portion 1112 extends in a direction that is generallyperpendicular, or perpendicular to the extending direction of thehorizontally extending aperture 1126. The apertures 1116, 1118, 1120,1122, 1124, 1126, which are disposed through the transducer beamportions 1106, 1108, 1110, 1112, significantly increase the sensitivityof the load transducer 1100 when a load is applied thereto by reducingthe cross-sectional area of the transducer beam portions 1106, 1108,1110, 1112 at the locations of the apertures 1116, 1118, 1120, 1122,1124, 1126.

As best shown in the perspective view of FIG. 39, the illustrated loadcells are located on the transducer beam portions 1106, 1108, 1110,1112. In the illustrated embodiment, each load cell comprises one ormore strain gages 1136, 1138, 1140. Specifically, in the illustratedembodiment, the first transducer beam portion 1106 of the loadtransducer 1100 comprises a strain gage 1136 disposed on a side surfacethereof that is sensitive to a first shear force component (i.e., aF_(Y) strain gage) and substantially centered on the aperture 1116. Inthe illustrated embodiment, the second transducer beam portion 1108 ofthe load transducer 1100 comprises a strain gage 1138 disposed on a sidesurface thereof that is sensitive to a second shear force component(i.e., a F_(X) strain gage) and substantially centered on the aperture1118. The second transducer beam portion 1108 also comprises a straingage 1140 disposed on a top surface thereof that is sensitive to avertical force component (i.e., a F_(Z) strain gage) and substantiallycentered on the aperture 1120. Also, in the illustrative embodiment, thethird transducer beam portion 1110 of the load transducer 1100 comprisesa strain gage 1136 disposed on a side surface thereof that is sensitiveto the first shear force component (i.e., a F_(Y) strain gage) andsubstantially centered on the aperture 1122. The fourth transducer beamportion 1112 of the load transducer 1100 comprises a strain gage 1138disposed on a side surface thereof that is sensitive to a second shearforce component (i.e., a F_(X) strain gage) and substantially centeredon the aperture 1124. The fourth transducer beam portion 1112 alsocomprises a strain gage 1140 disposed on a top surface thereof that issensitive to a vertical force component (i.e., a F_(Z) strain gage) andsubstantially centered on the aperture 1126. In the illustratedembodiment, the first shear force component is generally perpendicularto the second shear force component, and each of the first and secondshear force components are generally perpendicular to the vertical forcecomponent.

In the illustrated embodiment, the strain gages 1136, 1138, 1140 aredisposed on respective outer surfaces of the transducer beam portions1106, 1108, 1110, 1112. The outer surfaces of the transducer beamportions 1106, 1108, 1110, 1112 on which the strain gages 1136, 1138,1140 are disposed are generally opposite to the inner surfaces of therespective apertures 1116, 1118, 1120, 1122, 1124, 1126.

As best shown in FIGS. 39-41, the illustrated load cells are mounted onthe top and outer side surfaces of the transducer beam portions 1106,1108, 1110, 1112 of the load transducer 1100. Alternatively, the straingages 1136, 1138 can be mounted to the inner side surfaces of therespective first and second transducer beam portions 1106, 1108, ratherthan to the outer side surfaces of the respective first and secondtransducer beam portions 1106, 1108 as illustrated in FIGS. 39 and 40.Similarly, the strain gages 1136, 1138 can be mounted to the inner sidesurfaces of the respective third and fourth transducer beam portions1110, 1112, rather than to the outer side surfaces of the respectivethird and fourth transducer beam portions 1110, 1112 as illustrated inFIGS. 39 and 41. In addition, the strain gages 1140 can be mounted tothe bottom surfaces of the second and fourth transducer beam portions1108, 1112, rather than to the top of the transducer beam portions 1108,1112 as illustrated in FIGS. 39 and 41. In general, the strain gages1136, 1138, 1140 are mounted to surfaces generally normal to thedirection of applied vertical and/or shear forces (i.e., F_(X), F_(Y),F_(Z)). It is also noted that alternatively, strain gages 1136 can bemounted at both opposed side surfaces of first and third transducer beamportions 1106, 1110 and/or strain gages 1138 can be mounted at bothopposed side surfaces of the second and fourth transducer beam portions1108, 1112. Similarly, strain gages 1140 can be mounted at both the topsurface and the bottom surface of the second and fourth transducer beamportions 1108, 1112. These strain gages 1136, 1138, 1140 measure forceeither by bending moment or difference of bending moments at two crosssections. As force is applied to the central body portion 1102 of theload transducer 1100, the transducer beam portions bend. This bendingeither stretches or compresses the strain gages 1136, 1138, 1140, whichin turn changes the resistance of the electrical current passingtherethrough. The amount of change in the electrical voltage or currentis proportional to the magnitude of the applied force, as applied to thecentral body portion 1102 of the load transducer 1100. In theillustrated embodiment, each of the strain gages 1136, 1138, 1140comprises a full-bridge strain gage configuration (i.e., four (4) activestrain gage elements wired in a Wheatstone bridge configuration). In analternative embodiment, each of the strain gages 1136, 1138, 1140 maycomprise a half-bridge strain gage configuration (i.e., two (2) activestrain gage elements wired in a Wheatstone bridge configuration).

Turning again to FIGS. 39 and 41 of the illustrated embodiment, it canbe seen that the central body portion 1102 of the load transducer 1100comprises a plurality of mounting apertures 1142 (e.g., four apertures1142 arranged in 2×2 array) disposed therethrough for accommodatingfasteners (e.g., screws) that attach the load transducer 1100 to a firstobject, such as a plate component of a force plate or force measurementassembly (e.g., plate component 1152 in FIGS. 42 and 43). Also, asdepicted in FIGS. 39 and 41, the second and fourth transducer beamportions 1108, 1112 of the load transducer 1100 each comprise a mountingaperture 1144 (e.g., a single aperture 1144) disposed therethrough nearthe respective free ends 1108 a, 1112 a for accommodating a fastener(e.g., a screw) that attaches the load transducer 1100 to a secondobject, such as a mounting foot of a force plate or force measurementassembly. The load applied to the load transducer 1100 is conveyedthrough the plurality of beam portions 1106, 1108, 1110, 1112 of theload transducer 1100 from the first object (e.g., the plate component1152 in FIGS. 42 and 43) to the second object (e.g., the mounting footof the force measurement assembly).

In the illustrative embodiment of FIGS. 39-41, it can be seen that thecentral body portion 1102 of the load transducer 1100 comprises no otherapertures besides the mounting apertures 1142. That is, the central bodyportion 1102 is completely solid, except for the mounting apertures1142. Advantageously, the solid central body portion 1102 of the loadtransducer 1100 is structurally robust enough to support the load beingapplied to the object to which the load transducer 1100 is mounted(e.g., plate component 1152—see FIGS. 42 and 43) without undergoingexcessive deformation (i.e., without undergoing non-elasticdeformation).

An exemplary embodiment of a force measurement system is illustrated inFIGS. 42 and 43. In the illustrative embodiment, referring to FIG. 42,the force measurement system generally comprises a force measurementassembly 1150 (i.e., a force plate) that is operatively coupled to adata acquisition/data processing device 1174 (i.e., a data acquisitionand processing device or computing device that is capable of collecting,storing, and processing data). The force measurement assembly 1150illustrated in FIGS. 42 and 43 is configured to receive a subjectthereon, and is capable of measuring the forces and/or moments appliedto its measurement surface by the subject.

As shown in FIG. 42, the data acquisition and processing device 1174(e.g., in the form of a laptop digital computer) generally includes abase portion 1178 with a central processing unit (CPU) disposed thereinfor collecting and processing the data that is received from the forcemeasurement assembly 1150, and a plurality of devices 1180-1184operatively coupled to the central processing unit (CPU) in the baseportion 1178. Preferably, the devices that are operatively coupled tothe central processing unit (CPU) comprise user input devices 1180, 1182in the form of a keyboard 1180 and a touchpad 1182, as well as agraphical user interface in the form of a laptop LCD screen 1184. Whilea laptop type computing system is depicted in the embodiment of FIG. 42,one of ordinary skill in the art will appreciate that another type ofdata acquisition and processing device 1174 can be substituted for thelaptop computing system such as, but not limited to, a palmtop computingdevice (i.e., a PDA) or a desktop type computing system having aplurality of separate, operatively coupled components (e.g., a desktoptype computing system including a main housing with a central processingunit (CPU) and data storage devices, a remote monitor, a remotekeyboard, and a remote mouse).

As illustrated in FIG. 42, force measurement assembly 1150 isoperatively coupled to the data acquisition/data processing device 1174by virtue of an electrical cable 1176. In one embodiment of theinvention, the electrical cable 1176 is used for data transmission, aswell as for providing power to the force measurement assembly 1150.Various types of data transmission cables can be used for cable 1176.For example, the cable 1176 can be a Universal Serial Bus (USB) cable oran Ethernet cable. Preferably, the electrical cable 1176 contains aplurality of electrical wires bundled together, with at least one wirebeing used for power and at least another wire being used fortransmitting data. The bundling of the power and data transmission wiresinto a single electrical cable 1176 advantageously creates a simpler andmore efficient design. In addition, it enhances the safety of thetesting environment when human subjects are being tested on the forcemeasurement assembly 1150. However, it is to be understood that theforce measurement assembly 1150 can be operatively coupled to the dataacquisition/data processing device 1176 using other signal transmissionmeans, such as a wireless data transmission system. If a wireless datatransmission system is employed, it is preferable to provide the forcemeasurement assembly 1150 with a separate power supply in the form of aninternal power supply or a dedicated external power supply.

Referring again to FIG. 42, it can be seen that the force measurementassembly 1150 of the illustrated embodiment is in the form of a forceplate assembly with a single, continuous measurement surface. The forceplate assembly includes a plate component 1152 supported on a pluralityof load transducers 1100. As shown in FIGS. 42 and 43, the platecomponent 1152 comprises a top measurement surface 1154 (i.e., a planartop surface), a bottom surface 1164 disposed generally opposite to thetop measurement surface 1154, and a plurality of side surfaces 1156,1158, 1160, 1162 disposed between the top and bottom surfaces 1154,1164. In the illustrated embodiment, the first side surface 1156 of theplate component 1152 is disposed generally parallel to the second sidesurface 1158, and is disposed generally perpendicular to both the thirdside surface 1160 and the fourth side surface 1162. The third sidesurface 1160 of the plate component 1152 is disposed generally parallelto the fourth side surface 1162, and is disposed generally perpendicularto both the first side surface 1156 and the second side surface 1158.Turning to the exploded view of FIG. 43, it can be seen that the bottomsurface 1164 of the plate component 1152 comprises a plurality ofL-shaped transducer recesses 1166 formed therein. Each of the pluralityof transducer recesses 1166 corresponding to a footprint of either firstand second beam portions 1106, 1108 or third and fourth beam portions1110, 1112 of one of the plurality of load transducers 1100 so that theload measuring portions of the transducer beam portions 1106, 1108,1110, 1112 with strain gages 1136, 1138, 1140 are spaced apart frombottom surface of the plate component 1152 (i.e., so that the entireload is transferred through the transducer beam portions 1106, 1108,1110, 1112). Advantageously, the compact footprint of the loadtransducer 1100 enables the narrow force plate 1150 to be capable ofmeasuring all three components of the force (i.e., F_(X), F_(Y), F_(Z))applied to the plate component 1152 thereof.

In illustrated embodiment of FIGS. 42 and 43, the force measurementassembly 1150 comprises two (2) load transducers that are disposedunderneath, and near opposite ends of the plate component 1152.Advantageously, because the load transducers 1100 are compact, neitherof the load transducers 1100 extends substantially an entire length ofthe plate component 1152 of the force measurement assembly 1150. Thecompact construction of the load transducers 1100 not only reducesmaterial costs because less material is used to form the loadtransducers 1100, but it also allows the load transducers 1100 to beuniversally used on force plates having a myriad of different lengthsbecause it is not necessary for the load transducers 1100 to conform tothe footprint size of the force plate.

In other embodiments of the invention, rather than using a forcemeasurement assembly 1150 having a plate component 1152 with a singlemeasurement surface 1154, it is to be understood that a forcemeasurement assembly in the form of a dual force plate may bealternatively employed. Unlike the single force plate assembly 1150illustrated in FIGS. 42 and 43, the dual force plate comprises twoseparate plate components, each of which is configured to accommodate arespective one of a subject's feet thereon (i.e., the left platecomponent accommodates the subject's left foot, whereas the right platecomponent accommodates the subject's right foot). In these alternativeembodiments, each of the two plate components of the dual force plateare supported on two (2) load transducers 1100 (i.e., load transducers1100 are disposed at opposite ends of each of the two plate components).As such, the dual force plate comprises a total of four (4) loadtransducers 1100 (i.e., two (2) load transducers 1100 under each of thetwo plate components).

Now, turning to FIG. 37, it can be seen that the data acquisition/dataprocessing device 1174 (i.e., the laptop computing device) of the forcemeasurement system comprises a microprocessor 1174 a for processingdata, memory 1174 b (e.g., random access memory or RAM) for storing dataduring the processing thereof, and data storage device(s) 1174 c, suchas one or more hard drives, compact disk drives, floppy disk drives,flash drives, or any combination thereof. As shown in FIG. 37, the forcemeasurement assembly 1150 and the visual display device 1184 areoperatively coupled to the core components 1174 a, 1174 b, 1174 c of thedata acquisition/data processing device 1174 such that data is capableof being transferred between these devices 1150, 1174 a, 1174 b, 1174 c,and 1184. Also, as illustrated in FIG. 37, a plurality of data inputdevices 1180, 1182 such as the keyboard 1180 and mouse 1182 shown inFIG. 42, are operatively coupled to the core components 1174 a, 1174 b,1174 c of the data acquisition/data processing device 1174 so that auser is able to enter data into the data acquisition/data processingdevice 1174. In some embodiments, the data acquisition/data processingdevice 1174 can be in the form of a laptop computer, while in otherembodiments, the data acquisition/data processing device 1174 can beembodied as a desktop computer.

FIG. 38 graphically illustrates the acquisition and processing of theload data carried out by the exemplary force measurement system of FIG.42. Initially, as shown in FIG. 38, a load L is applied to the forcemeasurement assembly 1150 (e.g., by a subject disposed thereon). Theload is transmitted from the plate component 1152 to the loadtransducers 1100 disposed at each of the opposed ends of the platecomponent 1152. As described above, in the illustrated embodiment, eachof the load transducers 1100 includes a plurality of strain gages 1136,1138, 1140 wired in one or more Wheatstone bridge configurations,wherein the electrical resistance of each strain gage is altered whenthe associated beam portion of the load transducer 1100 undergoesdeformation resulting from the load (i.e., forces and/or moments) actingon the plate component 1152. For each plurality of strain gages disposedon the load transducers 1100, the change in the electrical resistance ofthe strain gages brings about a consequential change in the outputvoltage of the Wheatstone bridge (i.e., a quantity representative of theload being applied to the measurement surface 1154). Thus, in oneembodiment, the two (2) load transducers 1100 disposed under the platecomponent 1152 output a total of six (6) analog output voltages(signals). In some embodiments, the six (6) analog output voltages fromload transducers 1100 disposed under the plate component 1152 are thentransmitted to a preamplifier board (not shown) for preconditioning. Thepreamplifier board is used to increase the magnitudes of the transduceranalog voltages, and preferably, to convert the analog voltage signalsinto digital voltage signals as well. After which, the force measurementassembly 1150 transmits the force plate output signals S_(FP01)-S_(FP06)to a main signal amplifier/converter 1072. Depending on whether thepreamplifier board also includes an analog-to-digital (A/D) converter,the force plate output signals S_(FPO1)-S_(FP6) could be either in theform of analog signals or digital signals. The main signalamplifier/converter 1072 further magnifies the force plate outputsignals S_(FPO1)-S_(FPO6), and if the signals S_(FPO1)-S_(FP06) are ofthe analog-type (for a case where the preamplifier board did not includean analog-to-digital (A/D) converter), it may also convert the analogsignals to digital signals. Then, the signal amplifier/converter 1072transmits either the digital or analog signals S_(ACO1)-S_(AC06) to thedata acquisition/data processing device 1174 (computer 1174) so that theforces and/or moments that are being applied to the measurement surface1154 of the force measurement assembly 1150 can be transformed intooutput load values OL. In addition to the components 1174 a, 1174 b,1174 c, the data acquisition/data processing device 1174 may furthercomprise an analog-to-digital (A/D) converter if the signalsS_(ACO1)-S_(AC06) are in the form of analog signals. In such a case, theanalog-to-digital converter will convert the analog signals into digitalsignals for processing by the microprocessor 1174 a.

When the data acquisition/data processing device 1174 receives thevoltage signals S_(ACO1)-S_(ACO6), it initially transforms the signalsinto output forces by multiplying the voltage signals S_(ACO1)-S_(ACO6)by a calibration matrix. If a load transducer having moment strain gages(as shown in FIGS. 51-54) is used in conjunction with the forcemeasurement assembly 1150, the data acquisition/data processing devicemay additionally transform the signals into output moments bymultiplying the voltage signals by the calibration matrix. After which,the force exerted on the surface 1154 of the force measurement assembly1150, and the center of pressure of the applied force (i.e., the x and ycoordinates of the point of application of the force applied to themeasurement surface 1154) is determined by the data acquisition/dataprocessing device 1174. Referring to the perspective view of FIG. 42, itcan be seen that the center of pressure coordinates (x_(P) _(L) , y_(P)_(L) ) for the plate component 1152 of the force measurement assembly1150 are determined in accordance with x and y coordinate axes 1168,1170. In FIG. 42, the vertical component of the force (F_(Z)) is definedby the z coordinate axis 1172.

In one exemplary embodiment, the data acquisition/data processing device1174 determines all three (3) orthogonal components of the resultantforces acting on the plate component 1152 of the force measurementassembly 1150 (i.e., F_(X), F_(Y), F_(Z)). In yet other embodiments ofthe invention, all three (3) orthogonal components of the resultantforces and moments acting on the plate component 1152 of the forcemeasurement assembly 1150 (i.e., F_(X), F_(Y), F_(Z), M_(X), M_(Y),M_(Z)) may be determined (i.e., when the load transducer 1400 is used inlieu of the load transducers 1100).

FIGS. 44-46 illustrate a load transducer 1200 according to a fourteenthexemplary embodiment of the present invention. Referring initially tothe perspective view of FIG. 44, it can be seen that the load transducer1200 generally includes a one-piece compact transducer frame 1204 havinga central body portion 1202 and a plurality of beam portions 1206, 1208,1210, 1212 extending along sides 1202 a, 1202 b, 1202 c of the centralbody portion 1202. As best illustrated in the perspective view of FIG.44, each of the beam portions 1206, 1208, 1210, 1212 comprises one ormore load cells or transducer elements for measuring forces and/ormoments.

With reference again to FIG. 44, it can be seen that the illustratedcentral body portion 1202 is generally in the form of a rectangularprism with substantially right angle corners (i.e., substantially 90degree corners). In FIG. 44, it can be seen that the body portion 1202comprises a first pair of opposed sides 1202 a, 1202 c and a second pairof opposed sides 1202 b, 1202 d. The side 1202 a is disposed generallyparallel to the side 1202 c, while the side 1202 b is disposed generallyparallel to the side 1202 d. Each of the sides 1202 a, 1202 b, 1202 c,1202 d is disposed generally perpendicular to the planar top and bottomsurfaces of the body portion 1202. Also, each of the first pair ofopposed sides 1202 a, 1202 c is disposed generally perpendicular to eachof the second pair of opposed sides 1202 b, 1202 d. In addition, asshown in FIG. 44, the second side 1202 b comprises a beam connectingportion 1214 extending outward therefrom. In the illustrated embodiment,it can be seen that the beam connecting portion 1214 connects the beamportions 1206 and 1210 to the second side 1202 b of the central bodyportion 1202. In the illustrated embodiment, the total load applied tothe load transducer 1200 is transmitted through the beam portions 1206,1208, 1210, 1212.

As best shown in FIGS. 44 and 46, the proximal end of the first beamportion 1206 is rigidly connected to the central body portion 1202 bymeans of the beam connecting portion 1214, and the distal end of thefirst beam portion 1206 is rigidly connected to the proximal end of thesecond beam portion 1208. As depicted in these figures, the first beamportion 1206 extends along the second side 1202 b of the central bodyportion 1202, and the second beam portion 1208 extends along the firstside 1202 a of the central body portion 1202. More particularly, in theillustrative embodiment, the longitudinal axis of the first beam portion1206 is disposed generally parallel to the second side 1202 b of thecentral body portion 1202, and the longitudinal axis of the second beamportion 1208 is disposed generally parallel to the first side 1202 a ofthe central body portion 1202. As best shown in the perspective view ofFIG. 44, the top and bottom surfaces of each of the first and secondbeam portions 1206, 1208 are disposed substantially co-planar with thetop and bottom surfaces of the central body portion 1202. Also, in theillustrative embodiment, with reference again to FIGS. 44 and 46, thefirst beam portion 1206 is generally perpendicular, or perpendicular tothe second beam portion 1208 (i.e., together the first and second beamportions 1206, 1208 form an overall L-shaped beam arm). In addition, asshown in these figures, the first beam portion 1206 is spaced apart fromthe second side 1202 b of the central body portion 1202 by a first gap1228, and the second beam portion 1208 is spaced apart from the firstside 1202 a of the central body portion 1202 by a second gap 1230. Inthe illustrative embodiment, together the first gap 1228 and the secondgap 1230 form an overall L-shaped gap (i.e., the first gap 1228 isdisposed perpendicular to the second gap 1230).

Also, referring again to FIGS. 44 and 46, it can be seen that theproximal end of the third beam portion 1210 is rigidly connected to thecentral body portion 1202 by means of the beam connecting portion 1214,and the distal end of the third beam portion 1210 is rigidly connectedto the proximal end of the fourth beam portion 1212. As depicted inthese figures, the third beam portion 1210 extends along the second side1202 b of the central body portion 1202, and the fourth beam portion1212 extends along the third side 1202 c of the central body portion1202. More particularly, in the illustrative embodiment, thelongitudinal axis of the third beam portion 1210 is disposed generallyparallel to the second side 1202 b of the central body portion 1202, andthe longitudinal axis of the fourth beam portion 1212 is disposedgenerally parallel to the third side 1202 c of the central body portion1202. As best shown in the perspective view of FIG. 44, the top andbottom surfaces of each of the third and fourth beam portions 1210, 1212are disposed substantially co-planar with the top and bottom surfaces ofthe central body portion 1202. Also, in the illustrative embodiment,with reference again to FIGS. 44 and 46, the third beam portion 1210 isgenerally perpendicular, or perpendicular to the fourth beam portion1212 (i.e., together the third and fourth beam portions 1210, 1212 forman overall L-shaped beam arm). In addition, as shown in these figures,the third beam portion 1210 is spaced apart from the second side 1202 bof the central body portion 1202 by a third gap 1232, and the fourthbeam portion 1212 is spaced apart from the third side 1202 c of thecentral body portion 1202 by a fourth gap 1234. In the illustrativeembodiment, together the third gap 1232 and the fourth gap 1234 form anoverall L-shaped gap (i.e., the third gap 1232 is disposed perpendicularto the fourth gap 1234).

In the illustrative embodiment of FIGS. 44 and 46, unlike the embodimentof FIGS. 39-41, it can be seen that the free end 1208 a of the secondbeam portion 1208 is spaced apart from the fourth side 1202 d of thecentral body portion 1202 (i.e., the second beam portion 1208 extendsbeyond the fourth side 1202 d of the central body portion 1202). Also,as shown in FIGS. 44 and 46, the free end 1212 a of the fourth beamportion 1212 is spaced apart from the fourth side 1202 d of the centralbody portion 1202 (i.e., the fourth beam portion 1212 extends beyond thefourth side 1202 d of the central body portion 1202).

In the illustrative embodiment of FIGS. 44-46, the first beam portion1206 is provided with an aperture 1216 disposed therethrough, the secondbeam portion 1208 is provided with apertures 1218, 1220 disposedtherethrough, the third beam portion 1210 is provided with an aperture1222 disposed therethrough, and the fourth beam portion 1212 is providedwith apertures 1224, 1226 disposed therethrough. In particular, thefirst and third transducer beam portions 1206, 1210 are provided withrespective generally rectangular apertures 1216, 1222 disposedvertically through the beam portions 1206, 1210. The second transducerbeam portion 1208 is provided with a first generally rectangularaperture 1218 disposed vertically through the beam portion 1208 and asecond generally rectangular aperture 1220 disposed horizontally throughthe beam portion 1208. As such, the vertically extending aperture 1218of the second beam portion 1208 extends in a direction that is generallyperpendicular, or perpendicular to the extending direction of thehorizontally extending aperture 1220. Similarly, the fourth transducerbeam portion 1212 is provided with a first generally rectangularaperture 1224 disposed vertically through the beam portion 1212 and asecond generally rectangular aperture 1226 disposed horizontally throughthe beam portion 1212. As such, the vertically extending aperture 1224of the fourth beam portion 1212 extends in a direction that is generallyperpendicular, or perpendicular to the extending direction of thehorizontally extending aperture 1226. The apertures 1216, 1218, 1220,1222, 1224, 1226, which are disposed through the transducer beamportions 1206, 1208, 1210, 1212, significantly increase the sensitivityof the load transducer 1200 when a load is applied thereto by reducingthe cross-sectional area of the transducer beam portions 1206, 1208,1210, 1212 at the locations of the apertures 1216, 1218, 1220, 1222,1224, 1226.

As best shown in the perspective view of FIG. 44, the illustrated loadcells are located on the transducer beam portions 1206, 1208, 1210,1212. In the illustrated embodiment, each load cell comprises one ormore strain gages 1236, 1238, 1240. Specifically, in the illustratedembodiment, the first transducer beam portion 1206 of the loadtransducer 1200 comprises a strain gage 1236 disposed on a side surfacethereof that is sensitive to a first shear force component (i.e., aF_(Y) strain gage) and substantially centered on the aperture 1216. Inthe illustrated embodiment, the second transducer beam portion 1208 ofthe load transducer 1200 comprises a strain gage 1238 disposed on a sidesurface thereof that is sensitive to a second shear force component(i.e., a F_(X) strain gage) and substantially centered on the aperture1218. The second transducer beam portion 1208 also comprises a straingage 1240 disposed on a top surface thereof that is sensitive to avertical force component (i.e., a F_(Z) strain gage) and substantiallycentered on the aperture 1220. Also, in the illustrative embodiment, thethird transducer beam portion 1210 of the load transducer 1200 comprisesa strain gage 1236 disposed on a side surface thereof that is sensitiveto the first shear force component (i.e., a F_(Y) strain gage) andsubstantially centered on the aperture 1222. The fourth transducer beamportion 1212 of the load transducer 1200 comprises a strain gage 1238disposed on a side surface thereof that is sensitive to a second shearforce component (i.e., a F_(X) strain gage) and substantially centeredon the aperture 1224. The fourth transducer beam portion 1212 alsocomprises a strain gage 1240 disposed on a top surface thereof that issensitive to a vertical force component (i.e., a F_(Z) strain gage) andsubstantially centered on the aperture 1226. In the illustratedembodiment, the first shear force component is generally perpendicularto the second shear force component, and each of the first and secondshear force components are generally perpendicular to the vertical forcecomponent.

In the illustrated embodiment, the strain gages 1236, 1238, 1240 aredisposed on respective outer surfaces of the transducer beam portions1206, 1208, 1210, 1212. The outer surfaces of the transducer beamportions 1206, 1208, 1210, 1212 on which the strain gages 1236, 1238,1240 are disposed are generally opposite to the inner surfaces of therespective apertures 1216, 1218, 1220, 1222, 1224, 1226.

As best shown in FIGS. 44-46, the illustrated load cells are mounted onthe top and outer side surfaces of the transducer beam portions 1206,1208, 1210, 1212 of the load transducer 1200. Alternatively, the straingages 1236, 1238 can be mounted to the inner side surfaces of therespective first and second transducer beam portions 1206, 1208, ratherthan to the outer side surfaces of the respective first and secondtransducer beam portions 1206, 1208 as illustrated in FIGS. 44 and 45.Similarly, the strain gages 1236, 1238 can be mounted to the inner sidesurfaces of the respective third and fourth transducer beam portions1210, 1212, rather than to the outer side surfaces of the respectivethird and fourth transducer beam portions 1210, 1212 as illustrated inFIGS. 44 and 46. In addition, the strain gages 1240 can be mounted tothe bottom surfaces of the second and fourth transducer beam portions1208, 1212, rather than to the top of the transducer beam portions 1208,1212 as illustrated in FIGS. 44 and 45. In general, the strain gages1236, 1238, 1240 are mounted to surfaces generally normal to thedirection of applied vertical and/or shear forces (i.e., F_(X), F_(Y),F_(Z)). It is also noted that alternatively, strain gages 1236 can bemounted at both opposed side surfaces of first and third transducer beamportions 1206, 1210 and/or strain gages 1238 can be mounted at bothopposed side surfaces of the second and fourth transducer beam portions1208, 1212. Similarly, strain gages 1240 can be mounted at both the topsurface and the bottom surface of the second and fourth transducer beamportions 1208, 1212. These strain gages 1236, 1238, 1240 measure forceeither by bending moment or difference of bending moments at two crosssections. As force is applied to the central body portion 1202 of theload transducer 1200, the transducer beam portions bend. This bendingeither stretches or compresses the strain gages 1236, 1238, 1240, whichin turn changes the resistance of the electrical current passingtherethrough. The amount of change in the electrical voltage or currentis proportional to the magnitude of the applied force, as applied to thecentral body portion 1202 of the load transducer 1200. In theillustrated embodiment, each of the strain gages 1236, 1238, 1240comprises a full-bridge strain gage configuration (i.e., four (4) activestrain gage elements wired in a Wheatstone bridge configuration). In analternative embodiment, each of the strain gages 1236, 1238, 1240 maycomprise a half-bridge strain gage configuration (i.e., two (2) activestrain gage elements wired in a Wheatstone bridge configuration).

Turning again to FIGS. 44 and 46 of the illustrated embodiment, it canbe seen that the central body portion 1202 of the load transducer 1200comprises a plurality of mounting apertures 1242 (e.g., six apertures1242 arranged in 3×2 array) disposed therethrough for accommodatingfasteners (e.g., screws) that attach the load transducer 1200 to a firstobject, such as a plate component of a force plate or force measurementassembly (e.g., plate component 1152 in FIGS. 42 and 43). Also, asdepicted in FIGS. 44 and 46, the second and fourth transducer beamportions 1208, 1212 of the load transducer 1200 each comprise a mountingaperture 1244 (e.g., a single aperture 1244) disposed therethrough nearthe respective free ends 1208 a, 1212 a for accommodating a fastener(e.g., a screw) that attaches the load transducer 1200 to a secondobject, such as a mounting foot of a force plate or force measurementassembly. The load applied to the load transducer 1200 is conveyedthrough the plurality of beam portions 1206, 1208, 1210, 1212 of theload transducer 1200 from the first object (e.g., the plate component1152 in FIGS. 42 and 43) to the second object (e.g., the mounting footof the force measurement assembly).

In the illustrative embodiment of FIGS. 44-46, it can be seen that thecentral body portion 1202 of the load transducer 1200 comprises no otherapertures besides the mounting apertures 1242. That is, the central bodyportion 1202 is completely solid, except for the mounting apertures1242. Advantageously, the solid central body portion 1202 of the loadtransducer 1200 is structurally robust enough to support the load beingapplied to the object to which the load transducer 1100 is mounted(e.g., plate component of a force measurement assembly) withoutundergoing excessive deformation (i.e., without undergoing non-elasticdeformation).

FIGS. 47 and 48 illustrate a load transducer 1300, 1300′ according to afifteenth exemplary embodiment of the present invention. Referring tothe perspective view of FIG. 47, it can be seen that the load transducer1300 generally includes a one-piece compact transducer frame 1304 havinga central body portion 1302 and a plurality of beam portions 1306, 1308extending along sides 1302 a, 1302 b of the central body portion 1302.As best illustrated in the perspective view of FIG. 47, each of the beamportions 1306, 1308 comprises one or more load cells or transducerelements for measuring forces and/or moments. The load transducer 1300in FIG. 47 is configured for a left side mounting arrangement on a forcemeasurement assembly (e.g., the force measurement assembly 1340 in FIGS.49 and 50), whereas the load transducer 1300′ in FIG. 48 is configuredfor a right side mounting arrangement on a force measurement assembly(e.g., the force measurement assembly 1340 in FIGS. 49 and 50). Otherthan being configured for mounting on different sides of a forcemeasurement assembly, the load transducers 1300, 1300′ in FIGS. 47 and48 are generally the same.

With reference again to FIG. 47, it can be seen that the illustratedcentral body portion 1302 is generally in the form of a rectangularprism with substantially right angle corners (i.e., substantially 90degree corners). In FIG. 47, it can be seen that the body portion 1302comprises a first pair of opposed sides 1302 a, 1302 c and a second pairof opposed sides 1302 b, 1302 d. The side 1302 a is disposed generallyparallel to the side 1302 c, while the side 1302 b is disposed generallyparallel to the side 1302 d. Each of the sides 1302 a, 1302 b, 1302 c,1302 d is disposed generally perpendicular to the planar top and bottomsurfaces of the body portion 1302. Also, each of the first pair ofopposed sides 1302 a, 1302 c is disposed generally perpendicular to eachof the second pair of opposed sides 1302 b, 1302 d. In addition, asshown in FIG. 47, the second side 1302 b comprises a beam connectingportion 1310 extending outward therefrom. In the illustrated embodiment,it can be seen that the beam connecting portion 1310 connects the firstbeam portion 1306 to the second side 1302 b of the central body portion1302. In the illustrated embodiment, the total load applied to the loadtransducer 1300 is transmitted through the beam portions 1306, 1308.

As best shown in FIG. 47, the proximal end of the first beam portion1306 is rigidly connected to the central body portion 1302 by means ofthe beam connecting portion 1310, and the distal end of the first beamportion 1306 is rigidly connected to the proximal end of the second beamportion 1308. As depicted in these figures, the first beam portion 1306extends along the second side 1302 b of the central body portion 1302,and the second beam portion 1308 extends along the first side 1302 a ofthe central body portion 1302. More particularly, in the illustrativeembodiment, the longitudinal axis of the first beam portion 1306 isdisposed generally parallel to the second side 1302 b of the centralbody portion 1302, and the longitudinal axis of the second beam portion1308 is disposed generally parallel to the first side 1302 a of thecentral body portion 1302. As best shown in the perspective view of FIG.47, the top and bottom surfaces of each of the first and second beamportions 1306, 1308 are disposed substantially co-planar with the topand bottom surfaces of the central body portion 1302. Also, in theillustrative embodiment, with reference again to FIG. 47, the first beamportion 1306 is generally perpendicular, or perpendicular to the secondbeam portion 1308 (i.e., together the first and second beam portions1306, 1308 form an overall L-shaped beam arm). In addition, as shown inthis figure, the first beam portion 1306 is spaced apart from the secondside 1302 b of the central body portion 1302 by a first gap 1318, andthe second beam portion 1308 is spaced apart from the first side 1302 aof the central body portion 1302 by a second gap 1320. In theillustrative embodiment, together the first gap 1318 and the second gap1320 form an overall L-shaped gap (i.e., the first gap 1318 is disposedperpendicular to the second gap 1320). As shown in FIG. 48, the firstand second beam portions 1306′, 1308′ have the same configuration as thefirst and second beam portions 1306, 1308, except that the beam portions1306′, 1308′ of the load transducer 1300′ are configured for a rightside mounting arrangement on a force measurement assembly, rather thanthe left side mounting arrangement of the load transducer 1300.

In the illustrative embodiment of FIG. 47, like the embodiment of FIGS.39-41, it can be seen that the free end 1308 a of the second beamportion 1308 is generally aligned, or aligned with the fourth side 1302d of the central body portion 1302 (i.e., the end face of the secondbeam portion 1308 is co-planar with the fourth side 1302 d of thecentral body portion 1302). Similarly, as shown in FIG. 48, the free end1308 a′ of the second beam portion 1308′ of the load transducer 1300′ isgenerally aligned, or aligned with the fourth side 1302 d of the centralbody portion 1302 (i.e., the end face of the second beam portion 1308′is co-planar with the fourth side 1302 d of the central body portion1302).

In the illustrative embodiment of FIG. 47, the first beam portion 1306is provided with an aperture 1312 disposed therethrough, and the secondbeam portion 1308 is provided with apertures 1314, 1316 disposedtherethrough. In particular, the first transducer beam portion 1306 isprovided with a generally rectangular aperture 1312 disposed verticallythrough the beam portion 1306. The second transducer beam portion 1308is provided with a first generally rectangular aperture 1314 disposedvertically through the beam portion 1308 and a second generallyrectangular aperture 1316 disposed horizontally through the beam portion1308. As such, the vertically extending aperture 1314 of the second beamportion 1308 extends in a direction that is generally perpendicular, orperpendicular to the extending direction of the horizontally extendingaperture 1316. The apertures 1312, 1314, 1316, which are disposedthrough the transducer beam portions 1306, 1308, significantly increasethe sensitivity of the load transducer 1300 when a load is appliedthereto by reducing the cross-sectional area of the transducer beamportions 1306, 1308 at the locations of the apertures 1312, 1314, 1316.

As best shown in the perspective view of FIG. 47, the illustrated loadcells are located on the transducer beam portions 1306, 1308. In theillustrated embodiment, each load cell comprises one or more straingages 1322, 1324, 1326. Specifically, in the illustrated embodiment, thefirst transducer beam portion 1306 of the load transducer 1300 comprisesa strain gage 1322 disposed on a side surface thereof that is sensitiveto a first shear force component (i.e., a F_(Y) strain gage) andsubstantially centered on the aperture 1312. In the illustratedembodiment, the second transducer beam portion 1308 of the loadtransducer 1300 comprises a strain gage 1324 disposed on a side surfacethereof that is sensitive to a second shear force component (i.e., aF_(X) strain gage) and substantially centered on the aperture 1314. Thesecond transducer beam portion 1308 also comprises a strain gage 1326disposed on a top surface thereof that is sensitive to a vertical forcecomponent (i.e., a F_(Z) strain gage) and substantially centered on theaperture 1316. In the illustrated embodiment, the first shear forcecomponent is generally perpendicular to the second shear forcecomponent, and each of the first and second shear force components aregenerally perpendicular to the vertical force component.

In the illustrated embodiment, the strain gages 1322, 1324, 1326 aredisposed on respective outer surfaces of the transducer beam portions1306, 1308. The outer surfaces of the transducer beam portions 1306,1308 on which the strain gages 1322, 1324, 1326 are disposed aregenerally opposite to the inner surfaces of the respective apertures1312, 1314, 1316.

As best shown in FIG. 47, the illustrated load cells are mounted on thetop and outer side surfaces of the transducer beam portions 1306, 1308of the load transducer 1300. Alternatively, the strain gages 1322, 1324can be mounted to the inner side surfaces of the respective first andsecond transducer beam portions 1306, 1308, rather than to the outerside surfaces of the respective first and second transducer beamportions 1306, 1308 as illustrated in FIG. 47. In addition, the straingage 1326 can be mounted to the bottom surface of the second transducerbeam portion 1308, rather than to the top of the transducer beam portion1308 as illustrated in FIG. 47. In general, the strain gages 1322, 1324,1326 are mounted to surfaces generally normal to the direction ofapplied vertical and/or shear forces (i.e., F_(X), F_(Y), F_(Z)). It isalso noted that alternatively, strain gages 1322 can be mounted at bothopposed side surfaces of first transducer beam portion 1306 and/orstrain gages 1324 can be mounted at both opposed side surfaces of thesecond transducer beam portion 1308. Similarly, strain gages 1326 can bemounted at both the top surface and the bottom surface of the secondtransducer beam portion 1308. These strain gages 1322, 1324, 1326measure force either by bending moment or difference of bending momentsat two cross sections. As force is applied to the central body portion1302 of the load transducer 1300, the transducer beam portions bend.This bending either stretches or compresses the strain gages 1322, 1324,1326, which in turn changes the resistance of the electrical currentpassing therethrough. The amount of change in the electrical voltage orcurrent is proportional to the magnitude of the applied force, asapplied to the central body portion 1302 of the load transducer 1300. Inthe illustrated embodiment, each of the strain gages 1322, 1324, 1326comprises a full-bridge strain gage configuration (i.e., four (4) activestrain gage elements wired in a Wheatstone bridge configuration). In analternative embodiment, each of the strain gages 1322, 1324, 1326 maycomprise a half-bridge strain gage configuration (i.e., two (2) activestrain gage elements wired in a Wheatstone bridge configuration).

Turning again to FIG. 47 of the illustrated embodiment, it can be seenthat the central body portion 1302 of the load transducer 1300 comprisesa plurality of mounting apertures 1328 (e.g., four apertures 1328arranged in 2×2 array) disposed therethrough for accommodating fasteners(e.g., screws) that attach the load transducer 1300 to a first object,such as a plate component of a force plate or force measurement assembly(e.g., plate component 1342 in FIGS. 49 and 50). Also, as depicted inFIG. 47, the second transducer beam portion 1308 of the load transducer1300 comprises a mounting aperture 1330 (e.g., a single aperture 1330)disposed therethrough near the free end 1308 a thereof for accommodatinga fastener (e.g., a screw) that attaches the load transducer 1300 to asecond object, such as a mounting foot of a force plate or forcemeasurement assembly. The load applied to the load transducer 1300 isconveyed through the plurality of beam portions 1306, 1308 of the loadtransducer 1300 from the first object (e.g., the plate component 1342 inFIGS. 49 and 50) to the second object (e.g., the mounting foot of theforce measurement assembly).

In the illustrative embodiments of FIGS. 47 and 48, it can be seen thatthe central body portions 1302 of the load transducers 1300, 1300′comprise no other apertures besides the mounting apertures 1328. Thatis, the central body portion 1302 is completely solid, except for themounting apertures 1328. Advantageously, the solid central body portion1302 of the load transducer 1300, 1300′ is structurally robust enough tosupport the load being applied to the object to which the loadtransducer 1300, 1300′ is mounted (e.g., plate component 1342—see FIGS.49 and 50) without undergoing excessive deformation (i.e., withoutundergoing non-elastic deformation).

An exemplary embodiment of a force measurement assembly 1340 isillustrated in FIGS. 49 and 50. In the illustrative embodiment, theforce measurement assembly 1340 of FIGS. 49 and 50 may be provided aspart of a force measurement system, and thus may be operatively coupledto a data acquisition/data processing device (i.e., the dataacquisition/data processing device 1174 described in conjunction withFIG. 42 above). The functionality of the force measurement systemcomprising the force measurement assembly 1340 and the dataacquisition/data processing device would be generally the same as thatdescribed above for the embodiment of FIGS. 42 and 43, and thus need notbe reiterated in conjunction with the description of the forcemeasurement assembly 1340 of FIGS. 49 and 50. Also, like the forcemeasurement assembly 1150 described above, the force measurementassembly 1340 illustrated in FIGS. 49 and 50 is configured to receive asubject thereon, and is capable of measuring the forces and/or momentsapplied to its measurement surface by the subject.

Referring again to FIG. 49, it can be seen that the force measurementassembly 1340 of the illustrated embodiment is in the form of a forceplate assembly with a single, continuous measurement surface. The forceplate assembly includes a plate component 1342 supported on a pluralityof load transducers 1300, 1300′. As shown in FIGS. 49 and 50, the platecomponent 1342 comprises a top measurement surface 1344 (i.e., a planartop surface), a bottom surface 1354 disposed generally opposite to thetop measurement surface 1344, and a plurality of side surfaces 1346,1348, 1350, 1352 disposed between the top and bottom surfaces 1344,1354. In the illustrated embodiment, the first side surface 1346 of theplate component 1342 is disposed generally parallel to the second sidesurface 1348, and is disposed generally perpendicular to both the thirdside surface 1350 and the fourth side surface 1352. The third sidesurface 1350 of the plate component 1342 is disposed generally parallelto the fourth side surface 1352, and is disposed generally perpendicularto both the first side surface 1346 and the second side surface 1348.Turning to the exploded view of FIG. 50, it can be seen that the bottomsurface 1354 of the plate component 1342 comprises a plurality ofL-shaped transducer recesses 1356 formed therein. Each of the pluralityof transducer recesses 1356 corresponds to a footprint of the first andsecond beam portions 1306, 1308 of one of the plurality of loadtransducers 1300, 1300′ so that the load measuring portions of thetransducer beam portions 1306, 1308 with strain gages 1322, 1324, 1326are spaced apart from a bottom surface of the plate component 1342(i.e., so that the entire load is transferred through the transducerbeam portions 1306, 1308).

In illustrated embodiment of FIGS. 49 and 50, the force measurementassembly 1340 comprises a total of four (4) load transducers 1300, 1300′that are disposed underneath, and near each of the respective fourcorners (4) of the plate component 1342. As explained above, the loadtransducers 1300′ are generally the same as the load transducers 1300,expect that they are configured as a mirror image of the loadtransducers 1300. Advantageously, because the load transducers 1300,1300′ are compact, none of the plurality of load transducers 1300, 1300′extend substantially an entire length or width of the plate component1342 of the force measurement assembly 1340. The compact construction ofthe load transducers 1300, 1300′ not only reduces material costs becauseless material is used to form the load transducers 1300, 1300′, but italso allows the load transducers 1300, 1300′ to be universally used onforce plates having a myriad of different lengths and widths because itis not necessary for the load transducers 1300, 1300′ to conform to thefootprint size of the force plate.

In other embodiments of the invention, rather than using a forcemeasurement assembly 1340 having a plate component 1342 with a singlemeasurement surface 1344, it is to be understood that a forcemeasurement assembly in the form of a dual force plate may bealternatively employed. Unlike the single force plate assembly 1340illustrated in FIGS. 49 and 50, the dual force plate comprises twoseparate plate components, each of which is configured to accommodate arespective one of a subject's feet thereon (i.e., the left platecomponent accommodates the subject's left foot, whereas the right platecomponent accommodates the subject's right foot). In these alternativeembodiments, each of the two plate components of the dual force plateare supported on four (4) load transducers 1300, 1300′ (i.e., a loadtransducer 1300, 1300′ is disposed in each of the respective four (4)corners of each of the two plate components). As such, the dual forceplate comprises a total of eight (8) load transducers 1300, 1300′ (i.e.,four (4) load transducers 1300, 1300′ under each of the two platecomponents).

Similar to that described above for the force measurement assembly 1150,the force measurement assembly 1340 of FIGS. 49 and 50 is capable ofmeasuring all three (3) orthogonal components of the resultant forcesacting on the plate component 1342 of the force measurement assembly1340 (i.e., F_(X), F_(Y), F_(Z)). In yet other embodiments of theinvention, all three (3) orthogonal components of the resultant forcesand moments acting on the plate component 1342 of the force measurementassembly 1340 (i.e., F_(X), F_(Y), F_(Z), M_(X), M_(Y), M_(Z)) may bedetermined (i.e., when the load transducer 1400 is used in lieu of theload transducers 1300, 1300′). Also, referring to the perspective viewof FIG. 49, it can be seen that the center of pressure coordinates(x_(P) _(L) , y_(P) _(L) ) for the plate component 1342 of the forcemeasurement assembly 1340 may be determined in accordance with x and ycoordinate axes 1358, 1360. In FIG. 49, the vertical component of theforce (F_(Z)) is defined by the z coordinate axis 1362.

FIGS. 51-54 illustrate a load transducer 1400 according to a sixteenthexemplary embodiment of the present invention. Referring initially tothe perspective view of FIG. 51, it can be seen that the load transducer1400 generally includes a one-piece compact transducer frame 1404 havinga central body portion 1402 and beam portions 1406, 1408, 1410, 1412disposed on opposite sides 1402 a, 1402 c of the central body portion1402. As best illustrated in the perspective view of FIG. 51, each ofthe beam portions 1406, 1408, 1410, 1412 comprises one or more loadcells or transducer elements for measuring forces and/or moments.

With reference again to FIG. 51, it can be seen that the illustratedcentral body portion 1402 is generally in the form of rectangular prismwith substantially right angle corners (i.e., substantially 90 degreecorners). In FIG. 51, it can be seen that the body portion 1402comprises a first pair of opposed sides 1402 a, 1402 c and a second pairof opposed sides 1402 b, 1402 d. The side 1402 a is disposed generallyparallel to the side 1402 c, while the side 1402 b is disposed generallyparallel to the side 1402 d. Each of the sides 1402 a, 1402 b, 1402 c,1402 d is disposed generally perpendicular to the planar top and bottomsurfaces of the body portion 1402. Also, each of the first pair ofopposed sides 1402 a, 1402 c is disposed generally perpendicular to eachof the second pair of opposed sides 1402 b, 1402 d. In addition, asshown in FIG. 51, the first beam portion 1406 extends from the firstside 1402 a of the central body portion 1402 and the third beam portion1410 extends from the third side 1402 c of the central body portion1402. In the illustrated embodiment, the total load applied to the loadtransducer 1400 is transmitted through the beam portions 1406, 1408,1410, 1412.

As best shown in FIGS. 51 and 54, the proximal end of the first beamportion 1406 is rigidly connected to the first side 1402 a of thecentral body portion 1402, and the distal end of the first beam portion1406 is rigidly connected to the proximal end of the second beam portion1408. As depicted in these figures, the second beam portion 1408 extendsalong the first side 1402 a of the central body portion 1402. In theillustrative embodiment, the longitudinal axis of the first beam portion1406 is disposed generally perpendicular to the first side 1402 a of thecentral body portion 1402, and the longitudinal axis of the second beamportion 1408 is disposed generally parallel to the first side 1402 a ofthe central body portion 1402. As best shown in the perspective view ofFIG. 51, the top and bottom surfaces of each of the first and secondbeam portions 1406, 1408 are disposed substantially co-planar with thetop and bottom surfaces of the central body portion 1402. Also, in theillustrative embodiment, with reference again to FIGS. 51 and 54, thefirst beam portion 1406 is generally perpendicular, or perpendicular tothe second beam portion 1408 (i.e., together the first and second beamportions 1406, 1408 form an overall L-shaped beam arm). In addition, asshown in these figures, the second beam portion 1408 is spaced apartfrom the first side 1402 a of the central body portion 1402 by arectangular beam gap 1426.

Also, referring again to FIGS. 51 and 54, it can be seen that theproximal end of the third beam portion 1410 is rigidly connected to thethird side 1402 c of the central body portion 1402, and the distal endof the third beam portion 1410 is rigidly connected to the proximal endof the fourth beam portion 1412. As depicted in these figures, thefourth beam portion 1412 extends along the third side 1402 c of thecentral body portion 1402. In the illustrative embodiment, thelongitudinal axis of the third beam portion 1410 is disposed generallyperpendicular to the third side 1402 c of the central body portion 1402,and the longitudinal axis of the fourth beam portion 1412 is disposedgenerally parallel to the third side 1402 c of the central body portion1402. As best shown in the perspective view of FIG. 51, the top andbottom surfaces of each of the third and fourth beam portions 1410, 1412are disposed substantially co-planar with the top and bottom surfaces ofthe central body portion 1402. Also, in the illustrative embodiment,with reference again to FIGS. 51 and 54, the third beam portion 1410 isgenerally perpendicular, or perpendicular to the fourth beam portion1412 (i.e., together the third and fourth beam portions 1410, 1412 forman overall L-shaped beam arm). In addition, as shown in these figures,the fourth beam portion 1412 is spaced apart from the third side 1402 cof the central body portion 1402 by a rectangular beam gap 1428.

In the illustrative embodiment of FIGS. 51-54, like the embodiment ofFIGS. 39-41, it can be seen that the free end 1408 a of the second beamportion 1408 is generally aligned, or aligned with the fourth side 1402d of the central body portion 1402 (i.e., the end face of the secondbeam portion 1408 is co-planar with the fourth side 1402 d of thecentral body portion 1402). Also, as shown in FIGS. 51 and 54, the freeend 1412 a of the fourth beam portion 1412 is generally aligned, oraligned with the fourth side 1402 d of the central body portion 1402(i.e., the end face of the fourth beam portion 1412 is co-planar withthe fourth side 1402 d of the central body portion 1402).

In the illustrative embodiment of FIGS. 51-54, the first beam portion1406 is provided with an aperture 1414 disposed therethrough, the secondbeam portion 1408 is provided with apertures 1416, 1418 disposedtherethrough, the third beam portion 1410 is provided with an aperture1420 disposed therethrough, and the fourth beam portion 1412 is providedwith apertures 1422, 1424 disposed therethrough. In particular, thefirst and third transducer beam portions 1406, 1410 are provided withrespective generally rectangular apertures 1414, 1420 disposedvertically through the beam portions 1406, 1410. The second transducerbeam portion 1408 is provided with a first generally rectangularaperture 1416 disposed vertically through the beam portion 1408 and asecond generally rectangular aperture 1418 disposed horizontally throughthe beam portion 1408. As such, the vertically extending aperture 1416of the second beam portion 1408 extends in a direction that is generallyperpendicular, or perpendicular to the extending direction of thehorizontally extending aperture 1418. Similarly, the fourth transducerbeam portion 1412 is provided with a first generally rectangularaperture 1422 disposed vertically through the beam portion 1412 and asecond generally rectangular aperture 1424 disposed horizontally throughthe beam portion 1412. As such, the vertically extending aperture 1422of the fourth beam portion 1412 extends in a direction that is generallyperpendicular, or perpendicular to the extending direction of thehorizontally extending aperture 1424. The apertures 1414, 1416, 1418,1420, 1422, 1424, which are disposed through the transducer beamportions 1406, 1408, 1410, 1412, significantly increase the sensitivityof the load transducer 1400 when a load is applied thereto by reducingthe cross-sectional area of the transducer beam portions 1406, 1408,1410, 1412 at the locations of the apertures 1414, 1416, 1418, 1420,1422, 1424.

As best shown in the perspective view of FIG. 51, the illustrated loadcells are located on the transducer beam portions 1406, 1408, 1410,1412. In the illustrated embodiment, each load cell comprises one ormore strain gages 1430, 1432, 1434, 1436 a, 1436 b, 1438 a, 1438 b, 1440a, 1440 b. Specifically, in the illustrated embodiment, the firsttransducer beam portion 1406 of the load transducer 1400 comprises astrain gage 1430 disposed on a side surface thereof that is sensitive toa first shear force component (i.e., a F_(Y) strain gage) andsubstantially centered on the aperture 1414. The first transducer beamportion 1406 also comprises a first set of strain gages 1438 a, 1438 bthat are sensitive to a first moment component (i.e., a M_(Y) straingages). The strain gages 1438 a, 1438 b are disposed on opposed top andbottom surfaces of the first transducer beam portion 1406, and aresubstantially vertically aligned with one another. The first transducerbeam portion 1406 additionally comprises a second set of strain gages1440 a, 1440 b that are sensitive to a second moment component (i.e., aM_(Z) strain gages). The strain gages 1440 a, 1440 b are disposed onopposed side surfaces of the first transducer beam portion 1406, and aresubstantially horizontally aligned with one another. In the illustratedembodiment, the second transducer beam portion 1408 of the loadtransducer 1400 comprises a strain gage 1432 disposed on a side surfacethereof that is sensitive to a second shear force component (i.e., aF_(X) strain gage) and substantially centered on the aperture 1416. Thesecond transducer beam portion 1408 also comprises a strain gage 1434disposed on a top surface thereof that is sensitive to a vertical forcecomponent (i.e., a F_(Z) strain gage) and substantially centered on theaperture 1418. In addition, the second transducer beam portion 1408 alsocomprises a set of strain gages 1436 a, 1436 b that are sensitive to athird moment component (i.e., a M_(X) strain gages). The strain gages1436 a, 1436 b are disposed on opposed top and bottom surfaces of thesecond transducer beam portion 1408, and are substantially verticallyaligned with one another. Also, in the illustrative embodiment, thethird transducer beam portion 1410 of the load transducer 1400 comprisesa strain gage 1430 disposed on a side surface thereof that is sensitiveto the first shear force component (i.e., a F_(Y) strain gage) andsubstantially centered on the aperture 1420. The third transducer beamportion 1410 also comprises a first set of strain gages 1438 a, 1438 bthat are sensitive to a first moment component (i.e., a M_(Y) straingages). The strain gages 1438 a, 1438 b are disposed on opposed top andbottom surfaces of the third transducer beam portion 1410, and aresubstantially vertically aligned with one another. The third transducerbeam portion 1410 additionally comprises a second set of strain gages1440 a, 1440 b that are sensitive to a second moment component (i.e., aM_(Z) strain gages). The strain gages 1440 a, 1440 b are disposed onopposed side surfaces of the third transducer beam portion 1410, and aresubstantially horizontally aligned with one another. The fourthtransducer beam portion 1412 of the load transducer 1400 comprises astrain gage 1432 disposed on a side surface thereof that is sensitive toa second shear force component (i.e., a F_(X) strain gage) andsubstantially centered on the aperture 1422. The fourth transducer beamportion 1412 also comprises a strain gage 1434 disposed on a top surfacethereof that is sensitive to a vertical force component (i.e., a F_(Z)strain gage) and substantially centered on the aperture 1424. Inaddition, the fourth transducer beam portion 1412 also comprises a setof strain gages 1436 a, 1436 b that are sensitive to a third momentcomponent (i.e., a M_(X) strain gages). The strain gages 1436 a, 1436 bare disposed on opposed top and bottom surfaces of the fourth transducerbeam portion 1412, and are substantially vertically aligned with oneanother. In the illustrated embodiment, the first shear force componentis generally perpendicular to the second shear force component, and eachof the first and second shear force components are generallyperpendicular to the vertical force component.

In the illustrated embodiment, the strain gages 1430, 1432, 1434 aredisposed on respective outer surfaces of the transducer beam portions1406, 1408, 1410, 1412. The outer surfaces of the transducer beamportions 1406, 1408, 1410, 1412 on which the strain gages 1430, 1432,1434 are disposed are generally opposite to the inner surfaces of therespective apertures 1414, 1416, 1418, 1420, 1422, 1424.

As shown in FIGS. 51-54, the force component strain gages of theillustrated load cells are mounted on the top and outer side surfaces ofthe transducer beam portions 1406, 1408, 1410, 1412 of the loadtransducer 1400. Alternatively, the strain gages 1430, 1432 can bemounted to the inner side surfaces of the respective first and secondtransducer beam portions 1406, 1408, rather than to the outer sidesurfaces of the respective first and second transducer beam portions1406, 1408 as illustrated in FIGS. 51 and 54. Similarly, the straingages 1430, 1432 can be mounted to the inner side surfaces of therespective third and fourth transducer beam portions 1410, 1412, ratherthan to the outer side surfaces of the respective third and fourthtransducer beam portions 1410, 1412 as illustrated in FIGS. 51 and 54.In addition, the strain gages 1434 can be mounted to the bottom surfacesof the second and fourth transducer beam portions 1408, 1412, ratherthan to the top of the transducer beam portions 1408, 1412 asillustrated in FIGS. 51 and 54. In general, the strain gages 1430, 1432,1434 are mounted to surfaces generally normal to the direction ofapplied vertical and/or shear forces (i.e., F_(X), F_(Y), F_(Z)). It isalso noted that alternatively, strain gages 1430 can be mounted at bothopposed side surfaces of first and third transducer beam portions 1406,1410 and/or strain gages 1432 can be mounted at both opposed sidesurfaces of the second and fourth transducer beam portions 1408, 1412.Similarly, strain gages 1434 can be mounted at both the top surface andthe bottom surface of the second and fourth transducer beam portions1408, 1412. These strain gages 1430, 1432, 1434 measure force either bybending moment or difference of bending moments at two cross sections.As force is applied to the central body portion 1402 of the loadtransducer 1400, the transducer beam portions bend. This bending eitherstretches or compresses the strain gages 1430, 1432, 1434, which in turnchanges the resistance of the electrical current passing therethrough.The amount of change in the electrical voltage or current isproportional to the magnitude of the applied force, as applied to thecentral body portion 1402 of the load transducer 1400.

In the illustrated embodiment, each of the strain gages 1430, 1432, 1434comprises a full-bridge strain gage configuration (i.e., four (4) activestrain gage elements wired in a Wheatstone bridge configuration), whileeach of the strain gages 1436 a, 1436 b, 1438 a, 1438 b, 1440 a, and1440 b comprises a half-bridge strain gage configuration (i.e., two (2)active strain gage elements). Also, in the illustrative embodiment, thepair of strain gages 1436 a, 1436 b are wired together in one Wheatstonebridge configuration (i.e., with a total of four (4) active strain gageelements), the pair of strain gages 1438 a, 1438 b are wired together inanother Wheatstone bridge configuration (i.e., with a total of four (4)active strain gage elements), and the pair of strain gages 1440 a, 1440b are wired together in yet another Wheatstone bridge configuration(i.e., with a total of four (4) active strain gage elements).

Turning again to FIGS. 51 and 54 of the illustrated embodiment, it canbe seen that the central body portion 1402 of the load transducer 1400comprises a plurality of mounting apertures 1442 (e.g., four apertures1442 arranged in 2×2 array) disposed therethrough for accommodatingfasteners (e.g., screws) that attach the load transducer 1400 to a firstobject, such as a plate component of a force plate or force measurementassembly (e.g., plate component 1152 in FIGS. 42 and 43). Also, asdepicted in FIGS. 51 and 54, the second and fourth transducer beamportions 1408, 1412 of the load transducer 1400 each comprise a mountingaperture 1444 (e.g., a single aperture 1444) disposed therethrough nearthe respective free ends 1408 a, 1412 a for accommodating a fastener(e.g., a screw) that attaches the load transducer 1400 to a secondobject, such as a mounting foot of a force plate or force measurementassembly. The load applied to the load transducer 1400 is conveyedthrough the plurality of beam portions 1406, 1408, 1410, 1412 of theload transducer 1400 from the first object (e.g., the plate component1152 in FIGS. 42 and 43) to the second object (e.g., the mounting footof the force measurement assembly).

In the illustrative embodiment of FIGS. 51-54, it can be seen that thecentral body portion 1402 of the load transducer 1400 comprises no otherapertures besides the mounting apertures 1442. That is, the central bodyportion 1402 is completely solid, except for the mounting apertures1442. Advantageously, the solid central body portion 1402 of the loadtransducer 1400 is structurally robust enough to support the load beingapplied to the object to which the load transducer 1400 is mounted(e.g., a plate component of a force measurement assembly) withoutundergoing excessive deformation (i.e., without undergoing non-elasticdeformation).

Referring now to the drawings, FIGS. 55-60 illustrate a load transducer1510 according to a seventeenth exemplary embodiment of the presentinvention. As shown in these figures, in the illustrated embodiment, theload transducer 1510 is in the form of a pylon-type load cell. The loadtransducer 1510 generally includes a one-piece compact transducer frameportion having a central cylindrical body portion 1514 and a pair offlanges 1512, 1516 disposed at opposite longitudinal ends of the centralcylindrical body portion 1514. In particular, the load transducer 1510includes a bottom flange 1512 disposed at the lower longitudinal end ofthe cylindrical body portion 1514, and a top flange 1516 disposed at theupper longitudinal end of the cylindrical body portion 1514. As bestillustrated in the perspective view of FIG. 55 and the sectional view ofFIG. 60, the bottom flange 1512 comprises a plurality ofcircumferentially spaced-apart mounting apertures 1518 disposedtherethrough (e.g., eight (8) mounting apertures 1518 disposedtherethrough). Each of the mounting apertures 1518 is configured toreceive a respective fastener (e.g., a threaded screw or bolt) forsecuring the load transducer 1510 to an object (e.g., a bottom mountingplate). Similarly, as shown in FIG. 55 and top view of FIG. 59, the topflange 1516 also comprises a plurality of circumferentially spaced-apartmounting apertures 1526 disposed therethrough (e.g., eight (8) mountingapertures 1526 disposed therethrough). Each of the mounting apertures1526 is configured to receive a respective fastener (e.g., a threadedscrew or bolt) for securing the load transducer 1510 to an object (e.g.,a top plate member).

With reference to FIGS. 55, 59, and 60, it can be seen that, in theillustrative embodiment, the frame portion of the load transducer 1510includes a central aperture 1528 disposed therethrough in a longitudinaldirection of the load transducer 1510. As such, the central cylindricalbody portion 1514 of the load transducer 1510 is in the form of atubular member that undergoes elastic deformation when a load is appliedto the load transducer 1510. Advantageously, adding the central aperture1528 through the load transducer 1510 increases the sensitivity of theload transducer 1510.

In the illustrated embodiment, the frame portion of the load transducer1510 is milled as one solid and continuous piece of a single material.That is, the frame portion of the load transducer 1510 is of unitary orone-piece construction with the central cylindrical body portion 1514and the flanges 1512, 1516 integrally formed together. The frame portionof the load transducer 1510 is preferably machined in one piece fromaluminum, titanium, steel, or any other suitable material that meetsstrength and weight requirements. Alternatively, the central cylindricalbody portion 1514 of the load transducer 1510 may be formed separatelyfrom the flanges 1512, 1516, and then attached or joined to the flanges1512, 1516 in any suitable manner (e.g., by welding, etc.).

Referring collectively to FIGS. 55 and 60, it can be seen that aplurality of deformation sensing elements (e.g., strain gages 1520,1522, 1524) are disposed on the outer periphery of the centralcylindrical body portion 1514 of the load transducer 1510. Inparticular, in the illustrative embodiment, each of a first pair ofstrain gages 1520 (see FIG. 60) is sensitive to a first force component(i.e., the x-component of the force, F_(X)) of the load and outputs oneor more first output signals representative of the first force component(F_(X)). As best shown in the sectional view of FIG. 60, a first one ofthe strain gages 1520 is disposed opposite to a second one of the straingages 1520 across the longitudinal axis of the load transducer 1510. Inother words, the strain gages 1520 are spaced apart from one anotherabout the outer periphery of the central cylindrical body portion 1514by approximately 180 degrees.

With reference again to FIG. 60, in the illustrative embodiment, each ofa second pair of strain gages 1522 (see FIG. 60) is sensitive to atorsional moment component (i.e., the z-component of the moment, M_(Z))of the load and outputs one or more second output signals representativeof the torsional moment component (M_(Z)). As best shown in thesectional view of FIG. 60, like the strain gages 1520 described above, afirst one of the strain gages 1522 is disposed opposite to a second oneof the strain gages 1522 across the longitudinal axis of the loadtransducer 1510. In other words, the strain gages 1522 are spaced apartfrom one another about the outer periphery of the central cylindricalbody portion 1514 by approximately 180 degrees.

Turning again to FIG. 60, in the illustrative embodiment, each of athird pair of strain gages 1524 (see FIG. 60) is sensitive to a secondforce component (i.e., the y-component of the force, F_(Y)) of the loadand outputs one or more third output signals representative of thesecond force component (F_(Y)). As best shown in the sectional view ofFIG. 60, like the strain gages 1520 and 1522 described above, a firstone of the strain gages 1524 is disposed opposite to a second one of thestrain gages 1524 across the longitudinal axis of the load transducer1510. In other words, the strain gages 1524 are spaced apart from oneanother about the outer periphery of the central cylindrical bodyportion 1514 by approximately 180 degrees.

In the illustrated embodiment, each of the strain gages 1520, 1522, 1524comprise a half bridge (e.g., a half Wheatstone bridge). Although, inother embodiments, the strain gages 1520, 1522, 1524 may comprise a fullbridge (e.g., a full Wheatstone bridge). Also, in the illustratedembodiment, each of the strain gages 1520, 1522, 1524 may produce aseparate output signal (e.g., output voltage) such that the loadtransducer 1510 produces a total of six (6) total output signals (e.g.,output voltages). Although, in other embodiments, the paired straingages 1520, 1522, 1524 may be wired together such that the loadtransducer 1510 only produces a total of three (3) output signals (e.g.,output voltages).

FIGS. 61-66 illustrate a load transducer 1510′ according to aneighteenth exemplary embodiment of the present invention. As shown inthese figures, similar to the seventeenth illustrative embodiment, theload transducer 1510′ is in the form of a pylon-type load cell. As such,the load transducer 1510′ is similar in many respects to the loadtransducer 1510 of the seventeenth embodiment described above. However,unlike the aforedescribed load transducer 1510, the load transducer1510′ has an elongated central cylindrical body portion 1514′ withredundant sets of deformation sensing elements (e.g., strain gages 1530,1532, 1534) disposed above the primary sets of deformation sensingelements (e.g., strain gages 1520, 1522, 1524). Advantageously,providing the redundant sets of deformation sensing elements (e.g.,strain gages 1530, 1532, 1534) allow the load transducer 1510′ tofunction normally even if one of the strain gages were to fail. That is,the strain gages 1530, 1532, 1534 allow for redundant measurement of theforce components and torsional component in critical applications (e.g.,when the load transducer 1510′ is being used to control an importantindustrial process, etc.). Thus, advantageously, the redundant sets ofdeformation sensing elements (e.g., strain gages 1530, 1532, 1534) allowthe load transducer 1510′ to produce the same output when one of theprimary deformation sensing elements (e.g., strain gages 1520, 1522,1524) experiences a failure.

Referring collectively to FIGS. 61 and 66, it can be seen that redundantsets of deformation sensing elements (e.g., strain gages 1530, 1532,1534) are disposed on the outer periphery of the central cylindricalbody portion 1514′ of the load transducer 1510′ above the primary setsof deformation sensing elements (e.g., strain gages 1520, 1522, 1524).Similar to the strain gages 1520 described above, in the illustrativeembodiment, each of a first pair of redundant strain gages 1530 (seeFIG. 61) is sensitive to the first force component (i.e., thex-component of the force, F_(X)) of the load, and outputs one or morefirst output signals representative of the first force component(F_(X)). As best shown in the sectional view of FIG. 66, a first one ofthe strain gages 1530 is disposed opposite to a second one of the straingages 1530 across the longitudinal axis of the load transducer 1510′. Inother words, the strain gages 1530 are spaced apart from one anotherabout the outer periphery of the central cylindrical body portion 1514of the load transducer 1510′ by approximately 180 degrees.

With reference again to FIG. 66, similar to the strain gages 1522described above, in the illustrative embodiment, each of a second pairof redundant strain gages 1532 (see FIG. 61) is sensitive to thetorsional moment component (i.e., the z-component of the moment, M_(Z))of the load and outputs one or more second output signals representativeof the torsional moment component (M_(Z)). As best shown in thesectional view of FIG. 66, like the strain gages 1522 described above, afirst one of the redundant strain gages 1532 is disposed opposite to asecond one of the strain gages 1532 across the longitudinal axis of theload transducer 1510′. In other words, the strain gages 1532 are spacedapart from one another about the outer periphery of the centralcylindrical body portion 1514′ by approximately 180 degrees.

Turning again to FIG. 66, in the illustrative embodiment, each of athird pair of redundant strain gages 1534 (see FIG. 61) is sensitive tothe second force component (i.e., the y-component of the force, F_(Y))of the load, and outputs one or more third output signals representativeof the second force component (F_(Y)). As best shown in the sectionalview of FIG. 66, like the strain gages 1530 and 1532 described above, afirst one of the redundant strain gages 1534 is disposed opposite to asecond one of the strain gages 1534 across the longitudinal axis of theload transducer 1510′. In other words, the strain gages 1534 are spacedapart from one another about the outer periphery of the centralcylindrical body portion 1514′ by approximately 180 degrees.

Because the other features of the load transducer 1510′ have alreadybeen explained above in conjunction with the load transducer 1510, it isnot necessary to reiterate these features with respect to the loadtransducer 1510′. That is, the features that are common to both suchembodiments need not be repeated in conjunction with the description ofthe embodiment in FIGS. 61-66.

In the illustrated embodiments, each of the strain gages 1520, 1522,1524, 1530, 1532, 1534 comprise a half bridge (e.g., a half Wheatstonebridge). Although, in other embodiments, the strain gages 1520, 1522,1524, 1530, 1532, 1534 may comprise a full bridge (e.g., a fullWheatstone bridge). Also, in the illustrated embodiments, each of thestrain gages 1520, 1522, 1524, 1530, 1532, 1534 may produce a separateoutput signal (e.g., output voltage) such that the load transducer 1510′produces a total of twelve (12) total output signals (e.g., outputvoltages). Although, in other embodiments, the paired strain gages 1520,1522, 1524 may be wired together, and the paired strain gages 1530,1532, 1534 also may be wired together, such that the load transducer1510′ only produces a total of six (6) output signals (e.g., outputvoltages).

FIG. 67 graphically illustrates the acquisition and processing of theload data carried out by the exemplary load transducer data processingsystem. Initially, as shown in FIG. 67, a load L (e.g., forces and/ormoments) is applied to the load transducer 1510, 1510′. When theelectrical resistance of each strain gage 1520, 1522, 1524, 1530, 1532,1534 is altered by the application of the applied forces and/or moments,the change in the electrical resistance of the strain gages brings aboutconsequential changes in the output voltages of the strain gage bridgecircuits (e.g., a Wheatstone bridge circuits). Thus, in one embodiment,the three (3) pairs of strain gages 1520, 1522, 1524 output a total ofthree (3) analog output voltages (signals). In some embodiments, thethree (3) output voltages from the three (3) pairs of strain gages 1520,1522, 1524 are then transmitted to a preamplifier board (not shown) forpreconditioning. The preamplifier board is used to increase themagnitudes of the analog voltage signals, and preferably, to convert theanalog voltage signals into digital voltage signals as well. Afterwhich, the load transducer 1510, 1510′ transmits the output signalsS_(TO1)-S_(TO3) to a main signal amplifier/converter 1536. Depending onwhether the preamplifier board also includes an analog-to-digital (A/D)converter, the output signals S_(TO1)-S_(TO3) could be either in theform of analog signals or digital signals. The main signalamplifier/converter 1536 further magnifies the transducer output signalsS_(TO1)-S_(TO3), and if the signals S_(TO1)-S_(TO3) are of theanalog-type (for a case where the preamplifier board did not include ananalog-to-digital (A/D) converter), it may also convert the analogsignals to digital signals. Then, the signal amplifier/converter 1536transmits either the digital or analog signals S_(ACO1)-S_(ACO3) to thedata acquisition/data processing device 1538 (computer 1538) so that theforces and/or moments that are being applied to the load transducer1510, 1510′ can be transformed into output load values OL. The computeror data acquisition/data processing device 1538 may further comprise ananalog-to-digital (A/D) converter if the signals S_(ACO1)-S_(ACO3) arein the form of analog signals. In such a case, the analog-to-digitalconverter will convert the analog signals into digital signals forprocessing by the microprocessor of the computer 1538.

When the computer or data acquisition/data processing device 1538receives the voltage signals S_(ACO1)-S_(ACO3), it initially transformsthe signals into output forces and/or moments by multiplying the voltagesignals S_(ACO1)-S_(AC03) by a stored calibration matrix. After which,the force components F_(X), F_(Y) and the torsional moment componentM_(Z) applied to the load transducer 1510, 1510′ are determined by thecomputer or data acquisition/data processing device 1538. The manner inwhich the stored calibration matrix is utilized to eliminate crosstalkbetween the output signals or channels will be explained in furtherdetail hereinafter.

Now, turning to FIG. 68, it can be seen that the data acquisition/dataprocessing device 1538 (i.e., the computing device 1538) of the loadtransducer system 1550 comprises a microprocessor 1538 a for processingdata, memory 1538 b (e.g., random access memory or RAM) for storing dataduring the processing thereof, and data storage device(s) 1538 c, suchas one or more hard drives, compact disk drives, floppy disk drives,flash drives, or any combination thereof. As shown in FIG. 68, one ormore load transducers 1510, 1510′ and a visual display device 1544 areoperatively coupled to the core components 1538 a, 1538 b, 1538 c of thedata acquisition/data processing device 1538 such that data is capableof being transferred between these devices 1510, 1510′, 1538, and 1544.Also, as illustrated in FIG. 68, a plurality of data input devices 1540,1542 such as a keyboard 1540 and mouse 1542 are operatively coupled tothe core components 1538 a, 1538 b, 1538 c of the data acquisition/dataprocessing device 1538 so that a user is able to enter data into thedata acquisition/data processing device 1538. In some embodiments, thedata acquisition/data processing device 1538 can be in the form of alaptop computer, while in other embodiments, the data acquisition/dataprocessing device 1538 can be embodied as a desktop computer.

As will be described hereinafter, in the illustrative embodiment, thedata acquisition/data processing device 1538 is configured to utilizethe stored calibration matrix in order to substantially eliminatecrosstalk between the transducer output signals S_(TO1)-S_(TO3) so thatthe respective transducer output signals are generally representativeonly of a respective one of the force or moment components (F_(X),F_(Y), M_(Z)).

For example, initially referring to the signal flow diagram depicted inFIG. 69, the load L (t) applied to the transducer causes the deformationof the transducer strain gages. The response of the transducer to suchdeformation is denoted by the operator D in FIG. 69. The strain signalsfrom the strain gages are digitized into time-dependent raw load signalsB(t). Inherently, the strain signals are also a function of the appliedload: B(t) E B (L (t), t).

The transducer's operating conditions P(t) other than mechanical loads,such as temperatures, can have an effect on the transducer response

. They can also be collected and digitized into time-dependent auxiliarysignals A(t), subject to their own auxiliary response

_(P). In addition to temperature, operating conditions P(t) that canaffect the transducer response include the ambient pressure in theenvironment containing the load transducer, magnetic fields present inthe environment, and non-inertial conditions (i.e., accelerations otherthan gravitational acceleration).

When the transducer has a generally linear response to the applied load,and when the operating conditions P(t) are presumed to have a negligibleeffect on the transducer response, the calibrated load F(t) may bedetermined from the following equation:

F(t)=C·B(t)  (1)

where:

F(t): calibrated load;

C: calibration function; and

B(t): raw load.

Thus, using equation (1) above, the raw loads are calibrated using thecalibration function

to obtain the calibrated load F. The calibration function is the outcomeof a transducer calibration process.

In general, crosstalk in the raw load B is the linear dependence of anyone component of the raw load on more than one component of the appliedload L. Given a transducer with a linear response

such that rank(

)≧l (or l_(n)≧l), there exists a linear transformation CB such that CBL: it recovers and separates the individual components of the appliedload so that they become linearly independent. The linear independenceof the components of F is equivalent to lack of cross-talk.

For example, in one embodiment, a 2-axis sensor with two raw load signalcomponents and two calibrated load signal components is provided. Due tothe design of the transducer, each of the raw load signals is a linearcombination of both components of the load that are being sensed, asdescribed by the following two equations:

B ₁(t)=100F ₁(t)+100F ₂(t)  (2)

B ₂(t)=−100F ₁(t)+100F ₂(t)  (3)

The response

of this transducer is linear and given by the following matrix:

$\begin{matrix}{ = \begin{bmatrix}100 & 100 \\{- 100} & 100\end{bmatrix}} & (4)\end{matrix}$

Because both B₁ and B₂ carry a measure of F₁ and F₂, there is crosstalk.The following matrix separates these signals:

$\begin{matrix}{C = {^{- 1} = \begin{bmatrix}0.005 & {- 0.005} \\0.005 & 0.005\end{bmatrix}}} & (5)\end{matrix}$

Generally, for non-rectangular C and

, it holds that

·C≈I, where I is an identity matrix. In other words,

is a pseudoinverse of C.

Also, in the illustrative embodiment, data acquisition/data processingdevice 1538 is additionally configured to determine one or moredeformation compensation parameters for the load transducer system 1550and to correct the one or more respective output forces or moments usingthe one or more deformation compensation parameters. For example, withcombined reference to FIGS. 55 and 60, suppose that it is desired todetermine the x-component of the force (F_(X)) using the load transducer1510. As explained above, the pair of strain gages 1520 is sensitive tothe x-component of the force (F_(X)). However, because the transducerframe of the load transducer 1510 is not perfectly symmetrical (e.g.,due to machining imperfections) and the strain gages 1520, 1522, 1524are not perfectly positioned on the transducer frame of the loadtransducer 1510, the strain gages 1522, 1524, which are not designed tobe sensitive to the x-component of the force (F_(X)), will output anon-zero signal when only a force in the x-direction is applied to thepylon-type load transducer 1510. The data acquisition/data processingdevice 1538 may correct the load transducer output by using thefollowing equation:

F _(x)=(S _(x) ·A)+(S _(y) ·B)+(S _(T) ·C)  (6)

where:

-   -   F_(x): x-component of the force, which is the desired measured        quantity;    -   S_(x): signal from strain gages 1520 that are sensitive to the        x-component of the force;    -   A: calibration coefficient for the x-component of the force;    -   S_(y): signal from strain gages 1524 that are sensitive to the        y-component of the force;    -   B: calibration coefficient for the y-component of the force;    -   S_(T): signal from strain gages 1522 that are sensitive to the        torsional moment component (M_(Z)); and    -   C: calibration coefficient for the torsional moment component        (M_(Z)).        As such, the data acquisition/data processing device 1538 uses        the deformation output signals S_(y), S_(T) from the strain        gages 1522, 1524 in order to correct the x-component of the        force. That is, the terms (S_(y)·B) and (S_(T)·C) in        equation (6) are deformation compensation parameters that are        used to correct the x-component of the force so that the        imperfections in the machining of the frame portion of the load        transducer 1510 and the imperfect placement of the strain gages        may compensated for in the determination of the output force        (F_(X)), thereby resulting in a more accurate determination of        the output force (F_(X)).

In addition, in the illustrative embodiment, the data acquisition/dataprocessing device 1538 is further configured to determine one or moretemperature compensation parameters for the load transducer system 1550,and to correct the transducer output signals S_(TO1)-S_(TO3) using theone or more temperature compensation parameters. The dataacquisition/data processing device 1538 is further configured todetermine the respective force or moment components (F_(X), F_(Y),M_(Z)) from the respective transducer output signals S_(TO1)-S_(TO3).

In one or more embodiments, the load transducer 1510 further comprisesone or more temperature sensing elements 1546 disposed thereon (seeFIGS. 55, 56, and 58). For example, in some embodiments, the one or moretemperature sensing elements 1546 may comprise one or more thermistors.In other embodiments, one or more of the strain gages 1520, 1522, 1524may be used as the temperature sensing elements so that additionaltemperature sensing elements are not required. In these one or moreembodiments, the one or more temperature sensing elements are configuredto output one or more temperature output signals indicative of atemperature of at least a portion of the load transducer 1510. The oneor more temperature sensing elements are operatively coupled to the dataacquisition/data processing device 1538. The data acquisition/dataprocessing device 1538 is configured to receive the one or morerespective temperature output signals from the one or more temperaturesensing elements, and to determine the one or more temperaturecompensation parameters based upon the one or more respectivetemperature output signals for correcting the force and/or momentcomponents (F_(X), F_(Y), M_(Z)).

In one or more alternative embodiments, rather than using temperaturesensing elements to determine the temperature compensation parameters,the data processing device is configured to determine the one or moretemperature compensation parameters based upon the one or moreexcitation current values associated with the one or more deformationsensing elements (e.g., strain gages 1520, 1522, 1524) of the loadtransducer 1510. In these one or more alternative embodiments, the oneor more excitation current values may be determined by measuring theexcitation current of the strain gage bridge circuits of the loadtransducer 1510 (e.g., the current flowing through a particular one ofthe strain gages). The resistance of the strain gages 1520, 1522, 1524changes in accordance with the ambient temperature of the environment inwhich the load transducer 1510 is disposed.

In the illustrative embodiment, the data acquisition/data processingdevice 1538 may utilize the one or more temperature compensationparameters (as determined from either one or more temperature sensingelements or the one or more excitation current values) to correct fortemperature-induced effects on the zero drift of the load transducer1510. Also, in the illustrative embodiment, the data acquisition/dataprocessing device 1538 may utilize the one or more temperaturecompensation parameters to correct for temperature-induced effects onthe sensitivity of the load transducer 1510.

Further, in the illustrative embodiment, the data acquisition/dataprocessing device 1538 may be additionally configured to determine aposition of the applied load using the load transducer system 1550, andto correct the one or more output forces or moments based upon theposition of the applied load. In particular, as will be explainedhereinafter, in one or more embodiments, the data acquisition/dataprocessing device 1538 is configured to correct the one or more outputforces or moments of the load transducer system 1550 by utilizing amathematical relationship (e.g., a polynomial function) that is basedupon the position of the applied load.

In one or more embodiments, to correct for errors correlated to thepoint of application of the load, a nonlinear calibration function isutilized. There is a general form of such calibration function that iseasy to compute and is a good representation of the nonlinearitiestypical of transducers. First, the linear calibration function based onthe calibration matrix

, as usually used for calibration of load sensors, is

≡

B.  (7)

The generalized form of the calibration function uses a generalizationof the calibration matrix to a multivariate polynomial matrix

(B) of degree N on the elements of the raw load vector B:

≡

(B)B,  (8)

where each i, j-th element of the polynomial matrix

(B) is a general multivariate polynomial of degree N in each element ofB. Given a b-dimensional B, and

$c_{i,j,1},\ldots \;,c_{i,j,{(\begin{matrix}{b + N} \\b\end{matrix})}}$

are its coefficients, and the multivariate polynomial matrix's elementsare of the following degree-lexicographically ordered form, where thelexicographic order is on the elements of B:

$\begin{matrix}{{\mathbb{C}}_{i,j} = {c_{i,j,1} + {c_{i,j,2}B_{1}} + \ldots + {c_{i,j,{({b + 2})}}B_{1}^{2}} + \ldots + {c_{i,j,{({{Nb} + 1})}}B_{b}^{N}} + \ldots + {c_{i,j,{(\begin{matrix}{b + N} \\b\end{matrix})}}\left( {B_{1}^{N}\ldots \; B_{b}^{N}} \right)}}} & (9)\end{matrix}$

There are l·c·(_(b) ^(b+N)) polynomial coefficients in the polynomialmatrix

(B), where l is the dimension of the calibrated load vector F.

In practice, it is often sufficient to use a specialized form ofmultivariate polynomials, with some classes of the monomials having zerocoefficients. For example, a multivariate polynomial might include allsingle-variable terms up to N-th order, i.e. terms of the form B_(i)^(n), where n≦N, then all mixed terms of up to q variables up to M-thorder, i.e. of the form B_(i) ₁ ^(m) ¹ • . . . •B_(i) _(q) ^(m) ^(q) ,where m_(q) and i_(q) are the exponents and component indices in theq-th element of the term.

The multivariate polynomial calibration matrix elements can determinedduring the calibration process, by solving a linear system of equations

(B_(l))B_(l)=L_(l) for each l-th applied calibration load L_(l). Theunknowns are the values of coefficients c_(i,j,k), where i covers theindices of the applied load, j covers the indices of the raw load, and kcovers the indices of the multivariate polynomial of the chosendimension N. In practical applications, where the number of polynomialcoefficients to be determined is much smaller than the number of appliedcalibration points, the resulting coefficient vectors building up

are linear combinations of basis vectors, and further constraints areused to select a single scalar for each coefficient. Such constraint canbe e.g. a minimal-norm criterion for the vector of coefficients of

.

In one or more embodiments, to correct for errors correlated to theoperating conditions P, a nonlinear calibration function is utilized.The auxiliary signal A, representing the operating conditions, caninclude elements that are measures of any of the following: (i)temperature at one or more locations within the load sensor, (ii)resistance of one or more strain gage bridges, measured across theirexcitation voltage inputs, (iii) resistance of one or more strain gagehalf-bridges, either individual or forming a full bridge, measuredacross their excitation voltage inputs, (iv) atmospheric pressure, (v)components of magnetic field measured using a Hall sensor at one or morelocations within the load sensor, and (vi) components of magnetic fieldmeasured using sense coils and represented by the voltages induced inthese coils.

The generalized form of the calibration function uses a generalizationof the calibration matrix to a multivariate polynomial matrix

(A) of degree N on the elements of auxiliary signal vector A, used tocalibrate the raw load vector B:

≡

(A)B,  (10)

where each i, j-th element of the polynomial matrix

(A) is a general multivariate polynomial of degree N in each element ofA. Given an a-dimensional A, and its coefficients

$c_{i,j,1},\ldots \;,c_{i,j,{(\begin{matrix}{a + N} \\a\end{matrix})}},$

the multivariate polynomial matrix's elements are of the followingdegree-lexicographically ordered form, where the lexicographic order ison the elements of A:

$\begin{matrix}{{\mathbb{C}}_{i,j} = {c_{i,j,1} + {c_{i,j,2}A_{1}} + \ldots + {c_{i,j,{({a + 2})}}A_{1}^{2}} + \ldots + {c_{i,j,{({{Na} + 1})}}A_{a}^{N}} + \ldots + {{c_{i,j,{(\begin{matrix}{a + N} \\a\end{matrix})}}\left( {A_{1}^{N}\ldots \; A_{a}^{N}} \right)}.}}} & (11)\end{matrix}$

There are

$l \cdot c \cdot \begin{pmatrix}{a + N} \\a\end{pmatrix}$

polynomial coefficients in the polynomial matrix

(A), where l is the dimension of the calibrated load vector F. Themultivariate polynomial matrix of a sufficient degree corrects for bothzero drift and the sensitivity of the transducer.

In practice, it is often sufficient to use a specialized form ofmultivariate polynomials, with some classes of the monomials having zerocoefficients. For example, a multivariate polynomial might include allsingle-variable terms up to N-th order, i.e. terms of the form A_(i)^(n), where n≦N, then all mixed terms of up to q variables up to M-thorder, i.e. of the form A_(i) ₁ ^(m) ¹ • . . . •A_(i) _(q) ^(m) ^(q)where m_(q) and i_(q) are the exponents and component indices in theq-th element of the term.

The multivariate polynomial calibration matrix elements can bedetermined during the calibration process, by solving a linear system ofequations

(A_(l))B_(l)=L_(l) for each l-th applied calibration load L_(l), undersome conditions that resulted in A_(l). The unknowns are the values ofcoefficients c_(i,j,k), where i covers the indices of the applied load,j covers the indices of the raw load, and k covers the indices of themultivariate polynomial of the chosen dimension N. In practicalapplications, where the number of polynomial coefficients to bedetermined is much smaller than the number of applied calibrationpoints, the resulting coefficient vectors building up

are linear combinations of basis vectors, and further constraints areused to select a single scalar for each coefficient. Such constraint canbe e.g. a minimal-norm criterion for the vector of coefficients of

.

In one or more further embodiments, the load accuracy and operatingconditions corrections may be applied with their multivariate polynomialmatrices separated, first applying the load accuracy correctioncalibration, and then the operating conditions correction:

≡

₁(A)

₂(B)B.  (12)

Alternatively, the load accuracy and operating condition corrections canbe expressed using a single multivariate polynomial matrix on thecoefficients of both the auxiliary and raw load vectors:

≡

(A,B)B.  (13)

The multivariate polynomial calibration matrix

's elements can be determined during the calibration process, by solvinga linear system of equations

((A,B)_(l))B_(l)=L_(l) for each l-th applied calibration load L_(l),under some conditions where (A, B)_(l) is the concatenation of the rawload and auxiliary signal vectors. The unknowns are the values ofcoefficients c_(i,j,k), where i covers the indices of the applied load,j covers the indices of the concatenation of the raw load and auxiliarysignal vectors, and k covers the indices of the multivariate polynomialof the chosen dimension N. In practical applications, where the numberof polynomial coefficients to be determined is much smaller than thenumber of applied calibration points, the resulting coefficient vectorsbuilding up

are linear combinations of basis vectors, and further constraints areused to select a single scalar for each coefficient. Such constraint canbe e.g. a minimal-norm criterion for the vector of coefficients of

.

Any of the features or attributes of the above described embodiments andvariations can be used in combination with any of the other features andattributes of the above described embodiments and variations as desired.For example, any of the features or functionality described inconjunction with embodiments illustrated in FIGS. 55-68 (e.g.,temperature compensation or crosstalk elimination) may be utilized inthe embodiments of FIGS. 1-54.

It is apparent from the above detailed description that the presentinvention provides a low profile six-component load transducer 10, 10′,100, 200, 300, 400, 500, 600, 700, 800 which has a significant allowableoffset for the line of action of the force. In that, for a givenallowable maximum load, this load transducer has a much higher momentcapacity than currently available load transducers and the offset valuecan be as high as five times the diameter (or width dimension) of thetransducer. Therefore, the load transducer 10, 10′, 100, 200, 300, 400,500, 600, 700, 800 according to the present invention is able towithstand and measure moments which are approximately ten times higherthan that of a similarly sized and rated conventional load cell.

Also, it is readily apparent that the embodiments of the load transducer900, 1000, 1000′, 1100, 1200, 1300, 1300′, 1400 and the forcemeasurement assemblies 1040, 1150, 1340 using the same offer numerousadvantages and benefits. In particular, the load transducer 900, 1000,1000′, 1100, 1200, 1300, 1300′, 1400 described herein is capable ofbeing interchangeably used with a myriad of different force plate sizesso that load transducers that are specifically tailored for a particularforce plate size are unnecessary. Moreover, the universal loadtransducer 900, 1000, 1000′, 1100, 1200, 1300, 1300′, 1400 describedherein is compact and uses less stock material than conventional loadtransducers, thereby resulting in lower material costs. Also,advantageously, the load transducer 1100, 1200, 1300, 1300′ describedherein is easily machined using a single block of raw material (i.e., asingle block of aluminum) with very little waste because there are onlynarrow gaps between the central body portion and the transducer beamportions. Furthermore, the aforedescribed force measurement assemblies1040, 1150, 1340 utilize the compact and universal load transducer 900,1000, 1000′, 1100, 1200, 1300, 1300′, 1400 thereon so as to result in amore lightweight and portable force measurement assembly.

In addition, it is readily apparent that the embodiments of the loadtransducer system 1550 described above offer numerous advantages andbenefits. In particular, the load transducer system 1550 is capable ofcorrecting the output signal of a load transducer 1510, 1510′ so as toreduce or eliminate the effects of crosstalk among the channels of theload transducer 1510, 1510′. Moreover, the load transducer system 1550is capable of correcting the output signal of a load transducer 1510,1510′ so as to reduce or eliminate the effects of changes in temperatureon the output of the load transducer 1510, 1510′. Furthermore, the loadtransducer system 1550 is capable of accurately determining the appliedload regardless of the location of the applied load being measured bythe load transducer 1510, 1510′.

From the foregoing disclosure and detailed description of certainpreferred embodiments, it is also apparent that various modifications,additions and other alternative embodiments are possible withoutdeparting from the true scope and spirit of the present invention. Theembodiments discussed were chosen and described to provide the bestillustration of the principles of the present invention and itspractical application to thereby enable one of ordinary skill in the artto utilize the invention in various embodiments and with variousmodifications as are suited to the particular use contemplated. All suchmodifications and variations are within the scope of the presentinvention as determined by the appended claims when interpreted inaccordance with the benefit to which they are fairly, legally, andequitably entitled.

The invention claimed is:
 1. A load transducer system, comprising: aload transducer including: a load transducer frame portion, the loadtransducer frame portion configured to elastically deform when a load isapplied to the load transducer; and one or more deformation sensingelements disposed on the load transducer frame portion, the one or moredeformation sensing elements being sensitive to one or more respectiveforce or moment components of the load and outputting one or morerespective output signals representative of the one or more respectiveforce or moment components of the load; and a data processing deviceoperatively coupled to the one or more deformation sensing elements ofthe load transducer, the data processing device configured to receivethe one or more respective output signals from the one or moredeformation sensing elements, the data processing device furtherconfigured to determine one or more respective output forces or momentsfrom one or more respective output signals, and the data processingdevice additionally configured to determine one or more deformationcompensation parameters for the load transducer system and to correctthe one or more respective output forces or moments using the one ormore deformation compensation parameters.
 2. The load transducer systemaccording to claim 1, further comprising one or more additionaldeformation sensing elements disposed on the load transducer, the one ormore additional deformation sensing elements configured to output one ormore deformation output signals indicative of a deformation of a portionof the load transducer, the one or more additional deformation sensingelements being operatively to the data processing device, the dataprocessing device configured to receive the one or more respectivedeformation output signals from the one or more additional deformationsensing elements, and to determine the one or more deformationcompensation parameters based upon the one or more respectivedeformation output signals.
 3. The load transducer system according toclaim 2, wherein the one or more additional deformation sensing elementsof the load transducer comprise one or more strain gages configured tomeasure the deformation of the portion of the load transducer.
 4. Theload transducer system according to claim 1, wherein the load transducerframe portion is in the form of a load cell pylon, the load cell pylonbeing compact and of one-piece construction.
 5. The load transducersystem according to claim 1, wherein the data processing device isfurther configured to determine one or more temperature compensationparameters for the load transducer system and to correct at least one ofthe one or more respective output signals using the one or moretemperature compensation parameters, the data processing deviceadditionally configured to determine at least one output force or momentfrom the corrected one or more respective output signals of the one ormore deformation sensing elements of the load transducer.
 6. The loadtransducer system according to claim 1, further comprising one or moreredundant deformation sensing elements, the one or more redundantdeformation sensing elements configured to enable the load transducer toproduce the same output when one of the one or more deformation sensingelements experiences a failure.
 7. A load transducer system, comprising:a load transducer including: a load transducer frame portion, the loadtransducer frame portion configured to elastically deform when a load isapplied to the load transducer; and one or more deformation sensingelements disposed on the load transducer frame portion, the one or moredeformation sensing elements being sensitive to one or more respectiveforce or moment components of the load and outputting one or morerespective output signals representative of the one or more respectiveforce or moment components of the load; and a data processing deviceoperatively coupled to the one or more deformation sensing elements ofthe load transducer, the data processing device configured to receivethe one or more respective output signals from the one or moredeformation sensing elements, the data processing device furtherconfigured to determine one or more temperature compensation parametersfor the load transducer system and to correct the one or more respectiveoutput signals from the one or more deformation sensing elements usingthe one or more temperature compensation parameters, the data processingdevice additionally configured to determine one or more respectiveoutput forces or moments from one or more corrected respective outputsignals.
 8. The load transducer system according to claim 7, furthercomprising one or more temperature sensing elements disposed on the loadtransducer, the one or more temperature sensing elements configured tooutput one or more temperature output signals indicative of atemperature of at least a portion of the load transducer, the one ormore temperature sensing elements being operatively to the dataprocessing device, the data processing device configured to receive theone or more respective temperature output signals from the one or moretemperature sensing elements, and to determine the one or moretemperature compensation parameters based upon the one or morerespective temperature output signals.
 9. The load transducer systemaccording to claim 8, wherein the one or more temperature sensingelements comprise one or more thermistors.
 10. The load transducersystem according to claim 8, wherein the one or more temperature sensingelements comprise one or more strain gages.
 11. The load transducersystem according to claim 7, wherein the data processing device isfurther configured to determine one or more excitation current valuesassociated with the one or more deformation sensing elements of the loadtransducer, and to determine the one or more temperature compensationparameters based upon the one or more excitation current values.
 12. Theload transducer system according to claim 7, wherein the data processingdevice utilizes the one or more temperature compensation parameters tocorrect for temperature-induced effects on the zero drift of the loadtransducer.
 13. The load transducer system according to claim 7, whereinthe data processing device utilizes the one or more temperaturecompensation parameters to correct for temperature-induced effects onthe sensitivity of the load transducer.
 14. A load transducer system,comprising: a load transducer including: a load transducer frameportion, the load transducer frame portion configured to elasticallydeform when a load is applied to the load transducer; and one or moredeformation sensing elements disposed on the load transducer frameportion, the one or more deformation sensing elements being sensitive toone or more respective force or moment components of the load andoutputting one or more respective output signals representative of theone or more respective force or moment components of the load; and adata processing device operatively coupled to the one or moredeformation sensing elements of the load transducer, the data processingdevice configured to receive the one or more respective output signalsfrom the one or more deformation sensing elements, the data processingdevice further configured to reference a stored calibration matrix forthe load transducer, and to determine one or more output forces ormoments from the one or more respective output signals of the one ormore deformation sensing elements using the stored calibration matrix,the data processing device additionally configured to determine aposition of the applied load, and to correct the one or more outputforces or moments based upon the position of the applied load.
 15. Theload transducer system according to claim 14, wherein the dataprocessing device is configured to correct the one or more output forcesor moments by utilizing a mathematical relationship that is based uponthe position of the applied load.